Thermographic recording element

ABSTRACT

A thermographic recording element having at least one image forming layer contains an organic silver salt, a reducing agent, and optionally, a photosensitive silver halide. The element further contains a substituted alkene derivative of specific structure and preferably a specific hydrazine derivative. The element can be processed in a fully dry basis to produce images having high Dmax and gradation and free of black pepper.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a thermographic recording element and moreparticularly, to a photothermographic recording element suited for themanufacture of graphic printing plates.

2. Prior Art

Photothermographic materials which are processed by a photothermographicprocess to form photographic images are disclosed, for example, in U.S.Pat. Nos. 3,152,904 and 3,457,075, D. Morgan and B. Shely, “ThermallyProcessed Silver Systems” in “Imaging Processes and Materials,”Neblette, 8th Ed., Sturge, V. Walworth and A. Shepp Ed., page 2, 1969.

These photothermographic materials generally contain a reducible silversource (e.g., organic silver salt), a catalytic amount of aphotocatalyst (e.g., silver halide), a toner for controlling the tone ofsilver, and a reducing agent, typically dispersed in a binder matrix.Photothermographic materials are stable at room temperature. When theyare heated at an elevated temperature (e.g., 80° C. or higher) afterexposure, redox reaction takes place between the reducible silver source(functioning as an oxidizing agent) and the reducing agent to formsilver. This redox reaction is promoted by the catalysis of a latentimage produced by exposure. Silver formed by reaction of the organicsilver salt in exposed regions provides black images in contrast tounexposed regions, forming an image.

Such photothermographic materials have been used as microphotographicand radiographic photosensitive materials. However, only a few have beenused as a graphic printing photosensitive material because the imagequality is poor for the printing purpose as demonstrated by low maximumdensity (Dmax) and soft gradation.

With the recent advance of lasers and light-emitting diodes, scannersand image setters having an oscillation wavelength of 600 to 800 nm findwidespread use. There is a strong desire to have a high contrastphotosensitive material which has so high sensitivity and Dmax that itmay comply with such output devices. The demand for simple dryprocessing is also increasing.

U.S. Pat. No. 3,667,958 discloses that a photothermographic elementcomprising a polyhydroxybenzene combined with a hydroxylamine, reductoneor hydrazine has high image quality discrimination and resolution. Thiscombination of reducing agents, however, was found to incur an increaseof fog.

U.S. Pat. No. 5,496,695 discloses a heat-developable photothermographicelement comprising an organic silver salt, a silver halide, a hinderedphenol, and a certain hydrazine derivative. These hydrazine derivativeswere found still insufficient to accomplish a maximum ultimate densityor ultrahigh contrast.

U.S. Pat. No. 5,545,515 discloses the use of acrylonitriles as theco-developer. The hydrazine compounds used therein fail to achieve afully satisfactory high contrast while the occurrence of black pepperswas ascertained.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a thermographicrecording element having a high sensitivity and high Dmax and free ofblack peppers. Another object of the present invention is to provide aprinting plate-forming photosensitive element which can be processed ina fully dry basis without a need for wet processing and produce imagesof quality.

According to the invention, there is provided a thermographic recordingelement having at least one image forming layer. The element contains anorganic silver salt, a reducing agent, and at least one of substitutedalkene derivatives of the general formulae (1) through (14).

In formulae (1) through (14), W is an electron attractive group, D is anelectron donative group, and H is hydrogen. The groups represented by Wor D attached to the same carbon atom, taken together, may form a cyclicstructure. The compound may assume either a trans or a cis structurewhen both trans and cis structures are possible with respect to W or D.Two W groups in formula (14) form a cyclic structure.

In one preferred embodiment, the thermographic recording element furthercontains a hydrazine derivative of the general formula (I).

In formula (I), R² is an aliphatic, aromatic or heterocyclic group, R¹is hydrogen or a block group, G¹ is —CO—, —COCO—, —C(═S)—, —SO₂—, —SO—,—PO(R³)— or iminomethylene group, R³ is selected from the same range asdefined for R¹ and may be different from R¹, A¹ and A² are independentlyhydrogen, alkylsulfonyl, arylsulfonyl or acyl groups, at least one of A¹and A² is hydrogen, and letter m1 is equal to 0 or 1, with the provisothat R¹ is an aliphatic, aromatic or heterocyclic group when m1 is 0.

In one preferred embodiment, the thermographic recording element furthercontains a photosensitive silver halide so that the element may bephotosensitive. That is, a photothermographic (or photosensitive,heat-developable) recording element is provided.

DETAILED DESCRIPTION OF THE INVENTION

The thermographic (or heat-developable) recording element of theinvention has at least one image forming layer and contains an organicsilver salt and a reducing agent. Preferably it further contains aphotosensitive silver halide whereby the invention constitutes aphoto-thermographic (or photosensitive, heat-developable) recordingelement. According to the feature of the Invention, the element furthercontains substituted alkene derivatives of the general formulae (1)through (14). The inclusion of such substituted alkene derivatives notonly provides the thermographic recording element with a high Dmax, highsensitivity, and fully high contrast, but is also effective forsuppressing the occurrence of black peppers.

These advantages are enhanced by further adding a hydrazine derivativeof the general formula (I).

Substituted Alkene Derivative

First, the substituted alkene derivatives of the general formulae (1)through (14) are described in detail.

In formulae (1) through (14), W is an electron attractive group, D is anelectron donative group, and H is a hydrogen atom. The groupsrepresented by W or D attached to the same carbon atom, taken together,may form a cyclic structure. When both trans and cis structures arepossible with respect to W or D, the compound may assume either a transor a cis structure. Two W groups in formula (14) form a cyclicstructure.

In formulae (1) through (14), the electron attractive groups representedby W include halogen atoms, cyano groups, nitro groups, alkenyl groups,alkynyl groups, acyl groups, alkoxycarbonyl groups, aryloxycarbonylgroups, alkylsulfonyl groups, arylsulfonyl groups, carbamoyl groups,carbonamide groups, sulfamoyl groups, sulfonamide groups,trifluoromethyl groups, trichloromethyl groups, phosphoryl groups,carboxy groups (or salts thereof), sulfo groups (or salts thereof),heterocyclic groups, imino groups, and phenyl groups having suchelectron attractive groups as a substituent. These groups may havesubstituents, examples of which include halogen atoms (e.g., fluorine,chlorine, bromine and iodine atoms), alkyl groups (including aralkyl,cycloalkyl and active methine groups), alkenyl groups, alkynyl groups,aryl groups, heterocyclic groups, quaternized nitrogen atom-containingheterocyclic groups (such as pyridinio), acyl groups, alkoxycarbonylgroups, aryloxycarbonyl groups, carbamoyl groups, carboxy groups orsalts thereof, sulfonylcarbamoyl groups, acylcarbamoyl groups,sulfamoylcarbamoyl groups, carbazoyl groups, oxalyl groups, oxamoylgroups, cyano groups, thiocarbamoyl groups, hydroxy groups, alkoxygroups (including groups containing recurring ethyleneoxy orpropyleneoxy units), aryloxy groups, heterocyclic oxy groups, acyloxygroups, (alkoxy or aryloxy) carbonyloxy groups, carbamoyloxy groups,sulfonyloxy groups, amino groups, (alkyl, aryl or heterocyclic) aminogroups, N-substituted nitrogenous heterocyclic groups, acylamino groups,sulfonamide groups, ureido groups, thioureido groups, imide groups,(alkoxy or aryloxy) carbonylamino groups, sulfamoylamino groups,semicarbazide groups, thiosemicarbazide groups, hydrazino groups,quaternary ammonio groups, oxamoylamino groups, (alkyl or aryl)sulfonylureido groups, acylureido groups, acylsulfamoylamino groups,nitro groups, mercapto groups, (alkyl, aryl or heterocyclic) thiogroups, (alkyl or aryl) sulfonyl groups, (alkyl or aryl) sulfinylgroups, sulfo groups or salts thereof, sulfamoyl groups, acylsulfamoylgroups, sulfonylsulfamoyl groups or salts thereof, and phosphoramide orphosphate structure-bearing groups. These substituents may be furtherreplaced by other substituents selected from the foregoing examples.

The preferred electron attractive groups are those having 0 to 16 carbonatoms in total, especially 0 to 12 carbon atoms in total, for example,cyano, nitro, alkenyl, acyl, alkoxycarbonyl, aryloxycarbonyl,alkylsulfonyl, arylsulfonyl, carbamoyl, sulfamoyl, trifluoromethyl,phosphoryl groups, heterocyclic groups (5- and 6-membered heterocyclicgroups which may have a benzene or naphthalene ring fused thereto), andphenyl groups having any electron attractive group as a substituent. Itis noted that the heterocyclic groups in formulae (3) and (7) arenon-aromatic heterocyclic groups.

In formulae (1) through (14), the electron donative groups representedby D include hydroxy groups (or salts thereof), mercapto groups (orsalts thereof), alkoxy groups, aryloxy groups, heterocyclic oxy groups,alkylthio groups, arylthio groups, heterocyclic thio groups, aminogroups, alkylamino groups, arylamino groups, heterocyclic amino groups,and phenyl groups having such electron donative groups as a substituent.These groups may have substituents, examples of which are the same asdescribed for W.

The preferred electron donative groups are hydroxy groups (or saltsthereof), mercapto groups (or salts thereof), alkoxy groups, alkylthiogroups, arylthio groups, amino groups, alkylamino groups, arylaminogroups, and phenyl groups having any electron donative group as asubstituent.

Examples of the ring formed by W and D include saturated or unsaturated,carbocyclic or heterocyclic rings which may have a 4- to 6-membered ringfused thereto. Also the ring may be a cyclic ketone. The heterocyclicring preferably contains at least one atom of nitrogen, oxygen andsulfur, more preferably one or two such hetero atoms.

Preferred among the compounds of formulae (1) through (14) are those offormulae (1), (2), (3), (5), (7), (8), (10), (11), (12), (13), and (14).More preferred are the compounds of formulae (1), (2), (3), (5), (7),(8), (10), (11), (12), and (14).

Illustrative, non-limiting, examples of the compounds of formulae (1)through (14) are given below.

The compounds according to the invention can be readily synthesized bywell-known methods and are also commercially available from chemicalmanufacturers.

These compounds may be used alone or in admixture of two or more. Theamount of the compound(s) added is preferably 1×10⁻⁶ to 1 mol, morepreferably 1×10⁻⁵ to 5×10⁻¹ mol, and most preferably 2×10⁻⁵ to 2×10⁻¹mol per mol of silver. The compound may be added to an image forminglayer or any other layer on the image forming layer side of a support,and preferably to the image forming layer or a layer disposed adjacentthereto.

In the practice of the invention, the substituted alkene derivative isused as solution in water or a suitable organic solvent. Suitablesolvents include alcohols (e.g., methanol, ethanol, propanol, andfluorinated alcohols), ketones (e.g., acetone and methyl ethyl ketone),dimethylformamide, dimethylsulfoxide and methyl cellosolve.

A well-known emulsifying dispersion method is used for dissolving thesubstituted alkene derivative with the aid of an oil such as dibutylphthalate, tricresyl phosphate, glyceryl triacetate or diethyl phthalateor an auxiliary solvent such as ethyl acetate or cyclohexanone wherebyan emulsified dispersion is mechanically prepared. Alternatively, amethod known as a solid dispersion method is used for dispersing thesubstituted alkene derivative in powder form in water in a ball mill,colloidal mill or ultrasonic mixer.

Hydrazine Derivative

In the preferred embodiment, the thermographic recording element of theinvention contains a hydrazine derivative of the general formula (I).

Herein R² is an aliphatic, aromatic or heterocyclic group. R¹ ishydrogen or a block group. G¹ is —CO—, —COCO—, —C(═S)—, —SO₂—, —SO—,—PO(R³)— or iminomethylene group. R³ is selected from the same range asdefined for R¹ and may be different from R¹. A¹ and A² are bothhydrogen, or one of A¹ and A² is hydrogen and the other is a substitutedor unsubstituted alkylsulfonyl, substituted or unsubstitutedarylsulfonyl or substituted or unsubstituted acyl group. Letter m1 isequal to 0 or 1. R¹ is an aliphatic, aromatic or heterocyclic group whenm1 is 0.

In formula (I), the aliphatic groups represented by R² are preferablysubstituted or unsubstituted, normal, branched or cyclic alkyl, alkenyland alkynyl groups having 1 to 30 carbon atoms.

In formula (I), the aromatic groups represented by R² are preferablymonocyclic or fused ring aryl groups, for example, phenyl and naphthylgroups derived from benzene and naphthalene rings. The heterocyclicgroups represented by R² are preferably monocyclic or fused ring,saturated or unsaturated, aromatic or non-aromatic heterocyclic groupswhile the heterocycles in these groups include pyridine, pyrimidine,imidazole, pyrazole, quinoline, isoquinoline, benzimidazole, thiazole,benzothiazole, piperidine, triazine, morpholine, and piperazine rings.

Aryl, alkyl and aromatic heterocyclic groups are most preferred as R².

The group represented by R² may have a substituent. Exemplarysubstituents include halogen atoms (e.g., fluorine, chlorine, bromineand iodine), alkyl groups (inclusive of aralkyl, cycloalkyl and activemethine groups), alkenyl groups, alkynyl groups, aryl groups,heterocyclic groups, heterocyclic groups containing a quaternizednitrogen atom (e.g., pyridinio), acyl groups, alkoxycarbonyl groups,aryloxycarbonyl groups, carbamoyl groups, carboxy groups or saltsthereof, sulfonylcarbamoyl groups, acylcarbamoyl groups,sulfamoylcarbamoyl groups, carbazoyl groups, oxalyl groups, oxamoylgroups, cyano groups, thiocarbamoyl groups, hydroxy groups, alkoxygroups (inclusive of groups having recurring ethylenoxy or propylenoxyunits), aryloxy groups, heterocyclic oxy groups, acyloxy groups, (alkoxyor aryloxy)carbonyloxy groups, carbamoyloxy groups, sulfonyloxy groups,amino groups, (alkyl, aryl or heterocyclic) amino groups, N-substitutednitrogenous heterocyclic groups, acylamino groups, sulfon-amide groups,ureido groups, thioureido groups, imide groups, (alkoxy oraryloxy)carbonylamino groups, sulfamoyl-amino groups, semicarbazidegroups, thiosemicarbazide groups, hydrazino groups, quaternary ammoniogroups, oxamoylamino groups, (alkyl or aryl)sulfonylureido groups,acylureido groups, acylsulfamoylamino groups, nitro groups, mercaptogroups, (alkyl, aryl or heterocyclic) thio groups, (alkyl oraryl)sulfonyl groups, (alkyl or aryl)sulfinyl groups, sulfo groups orsalts thereof, sulfamoyl groups, acylsulfamoyl groups, sulfonylsulfamoylgroups or salts thereof, and groups containing a phosphoramide orphosphoric ester structure. These substituents may be furthersubstituted with such a substituent.

Preferred substituents that R² may have include, where R² is an aromaticor heterocyclic group, alkyl (inclusive of active methylene), aralkyl,heterocyclic, substituted amino, acylamino, sulfonamide, ureido,sulfamoylamino, imide, thioureido, phosphoramide, hydroxy, alkoxy,aryloxy, acyloxy, acyl, alkoxycarbonyl, aryloxycarbonyl, carbamoyl,carboxy (inclusive of salts thereof), (alkyl, aryl or heterocyclic)thio, sulfo (inclusive of salts thereof), sulfamoyl, halogen, cyano, andnitro groups.

Where R² is an aliphatic group, preferred substituents include alkyl,aryl, heterocyclic, amino, acylamino, sulfonamide, ureido,sulfamoylamino, imide, thioureido, phosphoramide, hydroxy, alkoxy,aryloxy, acyloxy, acyl, alkoxycarbonyl, aryloxycarbonyl, carbamoyl,carboxy (inclusive of salts thereof), (alkyl, aryl or heterocyclic)thio, sulfo (inclusive of salts thereof), sulfamoyl, halogen, cyano, andnitro groups.

In formula (I), R¹ is hydrogen or a block group. Examples of the blockgroup include aliphatic groups (e.g., alkyl, alkenyl and alkynylgroups), aromatic groups (monocyclic or fused ring aryl groups),heterocyclic groups, alkoxy, aryloxy, amino and hydrazino groups.

The alkyl groups represented by R¹ are preferably substituted orunsubstituted alkyl groups having 1 to 10 carbon atoms, for example,methyl, ethyl, trifluoromethyl, difluoromethyl,2-carboxytetrafluoroethyl, pyridiniomethyl, difluoromethoxymethyl,difluorocarboxymethyl, 3-hydroxy-propyl, hydroxymethyl,3-methanesulfonamidopropyl, benzenesulfonamidomethyl,trifluoroacetylmethyl, dimethyl-aminomethyl, phenylsulfonylmethyl,o-hydroxybenzyl, methoxymethyl, phenoxymethyl, 4-ethylphenoxymethyl,phenylthiomethyl, t-butyl, dicyanomethyl, diphenylmethyl,triphenylmethyl, methoxycarbonyldiphenylmethyl, cyano-diphenylmethyl,and methylthiodiphenylmethyl groups. The alkenyl groups are preferablythose having 1 to 10 carbon atoms, for example, vinyl,2-ethoxycarbonylvinyl, and 2-trifluoro-2-methoxycarbonylvinyl groups.The alkynyl groups are preferably those having 1 to 10 carbon atoms, forexample, ethynyl and 2-methoxycarbonylethynyl groups. The aryl groupsare preferably monocyclic or fused ring aryl groups, especially thosecontaining a benzene ring, for example, phenyl, perfluorophenyl,3,5-dichlorophenyl, 2-methanesulfonamidophenyl, 2-carbamoylphenyl,4,5-dicyano-phenyl, 2-hydroxymethylphenyl, 2,6-dichloro-4-cyanophenyl,and 2-chloro-5-octylsulfamoylphenyl groups.

The heterocyclic groups represented by R¹ are preferably 5- and6-membered, saturated or unsaturated, monocyclic or fused ring,heterocyclic groups containing at least one of nitrogen, oxygen andsulfur atoms, for example, morpholino, piperidino (N-substituted),imidazolyl, indazolyl (e.g., 4-nitroindazolyl), pyrazolyl, triazolyl,benzimidazolyl, tetrazolyl, pyridyl, pyridinio (e.g.,N-methyl-3-pyridinio), quinolinio, quinolyl, hydantoyl andimidazolidinyl groups.

The alkoxy groups are preferably those having 1 to 8 carbon atoms, forexample, methoxy, 2-hydroxyethoxy, benzyloxy, and t-butoxy groups. Thearyloxy groups are preferably substituted or unsubstituted phenoxygroups. The amino groups are preferably unsubstituted amino, alkylaminohaving 1 to 10 carbon atoms, arylamino, and saturated or unsaturatedheterocyclic amino groups (inclusive of nitrogenous heterocyclic aminogroups containing a quaternized nitrogen atom). Examples of the aminogroup include 2,2,6,6-tetramethylpiperidin-4-ylamino, propylamino,2-hydroxyethylamino, anilino, o-hydroxyanilino, 5-benzo-triazolylamino,and N-benzyl-3-pyridinioamino groups. The hydrazino groups arepreferably substituted or unsubstituted hydrazino groups and substitutedor unsubstituted phenylhydrazino groups (e.g.,4-benzenesulfonamidophenyl-hydrazino).

The groups represented by R¹ may be substituted ones, with examples ofthe substituent being as exemplified for the substituent on R².

In formula (I), R¹ may be such a group as to induce cyclization reactionto cleave a G¹—R¹ moiety from the remaining molecule to generate acyclic structure containing the atoms of the —G¹—R¹ moiety. Suchexamples are described in JP-A 29751/1988, for example.

The hydrazine derivative of formula (I) may have incorporated therein agroup capable of adsorbing to silver halide. Such adsorptive groupsinclude alkylthio, arylthio, thiourea, thioamide, mercapto heterocyclicand triazole groups as described in U.S. Pat. Nos. 4,385,108 and4,459,347, JP-A 195233/1984, 200231/1984, 201045/1984, 201046/1984,201047/1984, 201048/1984, 201049/1984, 170733/1986, 270744/1986,948/1987, 234244/1988, 234245/1988, and 234246/1988. These adsorptivegroups to silver halide may take the form of precursors. Such precursorsare exemplified by the groups described in JP-A 285344/1990.

R¹ and R² in formula (I) may have incorporated therein a ballast groupor polymer commonly used in immobile photographic additives such ascouplers. The ballast group is a group having at least 8 carbon atomsand relatively inert with respect to photographic properties. It may beselected from, for example, alkyl, aralkyl, alkoxy, phenyl, alkylphenyl,phenoxy, and alkylphenoxy groups. The polymer is exemplified in JP-A100530/1989, for example.

R¹ or R² in formula (I) may have a plurality of hydrazino groups as asubstituent. In this case, the compounds of formula (I) are polymericwith respect to hydrazino group. Exemplary polymeric compounds aredescribed in JP-A 86134/1989, 16938/1992, 197091/1993, WO 95-32452 and95-32453, Japanese Patent Application Nos. 351132/1995, 351269/1995,351168/1995, 351287/1995, and 351279/1995.

R¹ or R² in formula (I) may contain a cationic group (e.g., a groupcontaining a quaternary ammonio group and a nitrogenous heterocyclicgroup containing a quaternized nitrogen atom), a group containingrecurring ethyleneoxy or propyleneoxy units, an (alkyl, aryl orheterocyclic) thio group, or a group which is dissociable with a base(e.g., carboxy, sulfo, acylsulfamoyl, and carbamoylsulfamoyl). Exemplarycompounds containing such a group are described in, for example, in JP-A234471/1995, 333466/1993, 19032/1994, 19031/1994, 45761/1993,259240/1991, 5610/1995, and 244348/1995, U.S. Pat. Nos. 4,994,365 and4,988,604, and German Patent No. 4006032.

In formula (I), each of A¹ and A² is a hydrogen atom, a substituted orunsubstituted alkyl- or arylsulfonyl group having up to 20 carbon atoms(preferably a phenylsulfonyl group or a phenylsulfonyl group substitutedsuch that the sum of Hammette's substituent constants may be −0.5 ormore), or a substituted or unsubstituted acyl group having up to 20carbon atoms (preferably a benzoyl group, a benzoyl group substitutedsuch that the sum of Hammette's substituent constants may be −0.5 ormore, or a linear, branched or cyclic, substituted or unsubstituted,aliphatic acyl group wherein the substituent is selected from a halogenatom, ether group, sulfonamide group, carbonamide group, hydroxyl group,carboxy group and sulfo group). Most preferably, both A¹ and A² arehydrogen atoms.

The preferable range of the hydrazine derivatives of the general formula(I) is described.

In formula (I), R² is preferably phenyl, substituted alkyl of 1 to 3carbon atoms or aromatic heterocyclic groups.

Where R² represents phenyl or aromatic heterocyclic groups, preferredsubstituents thereon include nitro, cyano, alkoxy, alkyl, acylamino,ureido, sulfonamide, thioureido, carbamoyl, sulfamoyl, sulfonyl, carboxy(or salts thereof), sulfo (or salts thereof), alkoxycarbonyl, and chlorogroups.

Where R² represents substituted alkyl groups of 1 to 3 carbon atoms, itis more preferably substituted methyl groups, and further preferably di-or tri-substituted methyl groups. Exemplary preferred substituents onthese methyl groups include methyl, phenyl, cyano, (alkyl, aryl orheterocyclic) thio, alkoxy, aryloxy, chloro, heterocyclic,alkoxycarbonyl, aryloxycarbonyl, carbamoyl, sulfamoyl, amino, acylamino,and sulfonamide groups, and especially, substituted or unsubstitutedphenyl groups.

Where R² represents substituted methyl groups, preferred examplesthereof are t-butyl, dicyanomethyl, dicyanophenylmethyl, triphenylmethyl(trityl), diphenyl-methyl, methoxycarbonyldiphenylmethyl,cyanodiphenylmethyl, methylthiodiphenylmethyl, cyclopropyldiphenylmethylgroups, with trityl being most preferred.

Where R² represents heterocyclic groups, preferred examples thereof arepyridine, quinoline, pyrimidine, triazine, benzthiazole, benzimidazole,and thiophene rings.

Most preferably, R² in formula (I) represents substituted phenyl groups.

In formula (I), m1 is equal to 0 or 1. When m1 is 0, R¹ representsaliphatic, aromatic or heterocyclic groups. When m1 is 0, R¹ morepreferably represents phenyl groups, substituted alkyl groups of 1 to 3carbon atoms or alkenyl groups. Of these, the preferred ranges of thephenyl groups and the substituted alkyl groups of 1 to 3 carbon atomsare the same as the preferred range of R². Where R¹ represents alkenylgroups, they are preferably vinyl groups, more preferably vinyl groupshaving one or two substituents selected from cyano, acyl,alkoxycarbonyl, nitro, trifluoromethyl and carbamoyl groups. Exemplaryare 2,2-dicyanovinyl, 2-cyano-2-methoxycarbonylvinyl, and2-acetyl-2-ethoxycarbonylvinyl groups.

Preferably m1 is equal to 1.

Where R² is a phenyl or aromatic heterocyclic group and G¹ is —CO—, thegroups represented by R¹ are preferably selected from hydrogen, alkyl,alkenyl, alkynyl, aryl and heterocyclic groups, more preferably fromhydrogen, alkyl and aryl groups, and most preferably from hydrogen atomsand alkyl groups. Where R¹ represents alkyl groups, preferredsubstituents thereon are halogen, alkoxy, aryloxy, alkylthio, arylthio,hydroxy, sulfonamide, amino, acylamino, and carboxy groups.

Where R² is a substituted methyl group and G¹ is —CO—, the groupsrepresented by R¹ are preferably selected from hydrogen, alkyl, aryl,heterocyclic, alkoxy, and amino groups (including unsubstituted amino,alkylamino, arylamino and heterocyclic amino groups), more preferablyfrom hydrogen, alkyl, aryl, heterocyclic, alkoxy, alkylamino, arylamioand heterocyclic amino groups. Where G¹ is —COCO—, independent of R², R¹is preferably selected from alkoxy, aryloxy, and amino groups, morepreferably from substituted amino groups, specifically alkylamino,arylamino and saturated or unsaturated heterocyclic amino groups.

Where G¹ is —SO₂—, independent of R², R¹ is preferably selected fromalkyl, aryl and substituted amino groups.

In formula (I), G¹ is preferably —CO— or —COCO—, and most preferably—CO—.

Illustrative, non-limiting, examples of the compound represented byformula (I) are given below.

TABLE 1

R = X = —H —C₂F₄—COOH    or (—C₂F₄—COO^(⊖)K^(⊕))

1 3-NHCO—C₉H₁₉(n) 1a    1b 1c 1d 2

2a    2b 2c 2d 3

3a    3b 3c 3d 4

4a    4b 4c 4d 5

5a    5b 5c 5d 6

6a    6b 6c 6d 7 2,4-(CH₃)₂-3-SC₂H₄—(OC₂H₄)₄—OC₈H₁₇ 7a    7b 7c 7d

TABLE 2

R = X = —H —CF₂H

 8

 8a  8e  8f  8g  9 6-OCH₃-3-C₅H₁₁(t)  9a  9e  9f  9g 10

10a 10e 10f 10g 11

11a 11e 11f 11g 12

12a 12e 12f 12g 13

13a 13e 13f 13g 14

14a 14e 14f 14g

TABLE 3

X = Y = —CHO —COCF₃ —SO₂CH₃

15

15a 15h 15i 15j 16

16a 16h 16i 16j 17

17a 17h 17i 17j 18

18a 18h 18i 18j 19

19a 19h 19i 19j 20 3-NHSO₂NH—C₈H₁₇ 20a 20h 20i 20j 21

21a 21h 21i 21j

TABLE 4 R = —H —CF₃

22

22a 22h 22k 22l 23

23a 23h 23k 23l 24

24a 24h 24k 24l 25

25a 25h 25k 25l 26

26a 26h 26k 26l 27

27a 27h 27k 27l 28

28a 28h 28k 28l

TABLE 5

R = Y = —H —CH₂OCH₃

29

29a 29m 29n 29f 30

30a 30m 30n 30f 31

31a 31m 31n 31f 32 4-OH 32a 32m 32n 32f

33

33a 33m 33n 33f 34

34a 34m 34n 34f 35

35a 35m 35n 35f

TABLE 6

R = Y = —H —CF₂SCH₃ —CONHCH₃

36 2-NHSO₂CH₃— 36a 36o 36p 36q

37 2-OCH₃-4-NHSO₂C₁₂H₂₅ 37a 37o 37p 37q 38 3-NHCOC₁₁H₂₃-4-NHSO₂CF₃ 38a38o 38p 38q 39

39a 39o 39p 39q 40 4-OCO(CH₂)₂COOC₆H₁₃ 40a 40o 40p 40q 41

41a 41o 41p 41q 42

42a 42o 42p 42q

TABLE 7 43

44

45

46

47

48

49

50

TABLE 8 51

52

53

TABLE 9

R = Y = —H —CH₂OCH₃

—CONHC₃H₇ 54 2-OCH₃ 54a 54m 54r 54s 55 2-OCH₃ 55a 55m 55r 55s 5-C₈H₁₇(t)56 4-NO₂ 56a 56m 56r 56s 57 4-CH₃ 57a 57m 57r 57s 58

58a 58m 58r 58s 59

59a 59m 59r 59s

TABLE 10

R = Y = —H

60 2-OCH₃ 60a 60c 60f 60g 5-OCH₃ 61 4-C₈H₁₇(t) 61a 61c 61f 61g 62 4-OCH₃62a 62c 62f 62g 63 3-NO₂ 63a 63c 63f 63g 64

64a 64c 64f 64g 65

65a 65c 65f 65g

TABLE 11

R₂ = R₁ = —H

66

66a 66u 66v 66t 67

67a 67u 67v 67t 68

68a 68u 68v 68t 69

69a 69u 69v 69t 70

70a 70u 70v 70t 71

71a 71u 71v 71t

TABLE 12

R_(B) = R_(A) =

—OC₄H₉(t)

72

72s 72x 72y 72w 73

73s 73x 73y 73w 74

74s 74x 74y 74w 75

75s 75x 75y 75w 76

76s 76x 76y 76w

TABLE 13

R 77

78

79 —CH₂OCH₂CH₂SCH₂CH₂OCH₃ 80 —CF₂CF₂COOH 81

82

TABLE 14 83

84

85

86

87

88

TABLE 15 89

90

91

92

93

94

TABLE 16

R = Y =

—CH₂—Cl 95

95-1 95-2 95-3 95-4 96 4-COOH 96-1 96-2 96-3 96-4 97

97-1 97-2 97-3 97-4 98

98-1 98-2 98-3 98-4 99

99-1 99-2 99-3 99-4 100

100-1  100-2  100-3  100-4 

TABLE 17

X =                 Y =

101 4-NO 101-5 101-6 101-7 101y 102 2,4-OCH₃ 102-5 102-6 102-7 102y 103

103-5 103-6 103-7 103y X =                 Y =

104

104-8 104-9 104w¹ 104x 105

105-8 105-9 105w¹ 105x

TABLE 18 Y—NHNH —X X = Y =

106

106-10 106a 106m 106y 107

107-10 107a 107m 107y 108

108-10 108a 108m 108y 109

109-10 109a 109m 109y 110

110-10 110a 110m 110y 111

111-11 111a 111m 111y

TABLE 19 Y—NHNH—X X = Y =

112

112-11 112-12 112-13 112-14 113

113-11 113-12 113-13 113-14 114

114-11 114-12 114-13 114-14 115

115-11 115-12 115-13 115-14 116

116-11 116-12 116-13 116-14 117

117-11 117-12 117-13 117-14

TABLE 20 118

119

120

121

122

123

TABLE 21

X = Ar = —OH —SH —NHCOCF₃ —NHSO₂CH₃ —NHSO₂ph —N(CH₃)₂ 124

124a 124b 124c 124d 124e 124f 125

125a 125b 125c 125d 125e 125f 126

126a 126b 126c 126d 126e 126f 127

127a 127b 127c 127d 127e 127f 128

128a 128b 128c 128d 128e 128f 129

129a 129b 129c 129d 129e 129f 130

130a 130b 130c 130d 130e 130f 131

131a 131b 131c 131d 131e 131f 132

132a 132b 132c 132d 132e 132f 133

133a 133b 133c 133d 133e 133f 134

134a 134b 134c 134d 134e 134f

TABLE 22 135

136

137

138

139

140

The compounds of formula (I) may be used alone or in admixture of two ormore.

In addition to the above-described ones, the following hydrazinederivatives are also preferable for use in the practice of theinvention. If desired, any of the following hydrazine derivatives may beused in combination with the hydrazine derivatives of formula (I). Thehydrazine derivatives which are used herein can be synthesized byvarious methods as described in the following patents.

Exemplary hydrazine derivatives which can be used herein include thecompounds of the chemical formula [1] in JP-B 77138/1994, morespecifically the compounds described on pages 3 and 4 of the same; thecompounds of the general formula (I) in JP-B 93082/1994, morespecifically compound Nos. 1 to 38 described on pages 8 to 18 of thesame; the compounds of the general formulae (4), (5) and (6) in JP-A230497/1994, more specifically compounds 4-1 to 4-10 described on pages25 and 26, compounds 5-1 to 5-42 described on pages 28 to 36, andcompounds 6-1 to 6-7 described on pages 39 and 40 of the same; thecompounds of the general formulae (1) and (2) in JP-A 289520/1994, morespecifically compounds 1-1 to 1-17 and 2-1 described on pages 5 to 7 ofthe same; the compounds of the chemical formulae [2] and [3] in JP-A313936/1994, more specifically the compounds described on pages 6 to 19of the same; the compounds of the chemical formula [1] in JP-A313951/1994, more specifically the compounds described on pages 3 to 5of the same; the compounds of the general formula (I) in JP-A 5610/1995,more specifically compounds I-1 to I-38 described on pages 5 to 10 ofthe same; the compounds of the general formula (II) in JP-A 77783/1995,more specifically compounds II-1 to II-102 described on pages 10 to 27of the same; the compounds of the general formulae (H) and (Ha) in JP-A104426/1995, more specifically compounds H-1 to H-44 described on pages8 to 15 of the same; the compounds having an anionic group in proximityto a hydrazine group or a nonionic group capable of forming anintramolecular hydrogen bond with the hydrogen atom of hydrazinedescribed in EP 713131A, especially compounds of the general formulae(A), (B), (C), (D), (E), and (F), more specifically compounds N-1 toN-30 described therein; and the compounds of the general formula (1) inEP 713131A, more specifically compounds D-1 to D-55 described therein.

Also useful are the hydrazine derivatives described in “KnownTechnology,” Aztech K.K., Mar. 22, 1991, pages 25-34 and Compounds D-2and D-39 described in JP-A 86354/1987, pages 6-7.

In the practice of the invention, the hydrazine nucleating agent is usedas solution in water or a suitable organic solvent. Suitable solventsinclude alcohols (e.g., methanol, ethanol, propanol, and fluorinatedalcohols), ketones (e.g., acetone and methyl ethyl ketone),dimethylformamide, dimethylsulfoxide and methyl cellosolve.

A well-known emulsifying dispersion method is used for dissolving thehydrazine derivative with the aid of an oil such as dibutyl phthalate,tricresyl phosphate, glyceryl triacetate or diethyl phthalate or anauxiliary solvent such as ethyl acetate or cyclohexanone whereby anemulsified dispersion is mechanically prepared. Alternatively, a methodknown as a solid dispersion method is used for dispersing the hydrazinederivative in powder form in water in a ball mill, colloidal mill orultrasonic mixer.

The hydrazine nucleating agent may be added to an image forming layer orany other layer on the image forming layer side of a support, andpreferably to the image forming layer or a layer disposed adjacentthereto.

The hydrazine nucleating agent is preferably used in an amount of 1×10⁻⁶mol to 1 mol, more preferably 1×10⁵ mol to 5×10⁻¹ mol, and mostpreferably 2×10⁻⁵ mol to 2×10⁻¹ mol per mol of silver.

In the thermographic recording element of the invention, a nucleationpromoter may be added in combination with the hydrazine derivative. Thenucleation promoter used herein includes amine derivatives, onium salts,disulfide derivatives, and hydroxylamine derivatives.

Examples of the nucleation promoter are shown below.

Other useful examples of the nucleation promoter include the compoundsdescribed in JP-A 77783/1995, page 48, lines 2-37, more specificallyCompounds A-1 to A-73 described on pages 49-58 of the same; thecompounds of the chemical formulae [21], [22] and [23] described in JP-A84331/1995, more specifically the compounds described on pages 6-8 ofthe same; the compounds of the general formulae [Na] and [Nb] describedin JP-A 104426/1995, more specifically Compounds Na-1 to Na-22 and Nb-1to Nb-12 described on pages 16-20 of the same; the compounds of thegeneral formulae (1), (2), (3), (4), (5), (6) and (7) described in JP-A37817/1995, more specifically Compounds 1-1 to 1-19, Compounds 2-1 to2-22, Compounds 3-1 to 3-36, Compounds 4-1 to 4-5, Compounds 5-1 to5-41, Compounds 6-1 to 6-58 and Compounds 7-1 to 7-38 described therein;and the nucleation promoters described in Japanese Patent ApplicationNo. 70908/1996.

The nucleation promoter is preferably used in an amount of 1×10⁻⁶ mol to2×10⁻² mol, more preferably 1×10⁻⁵ mol to 2×10⁻² mol, and mostpreferably 2×10⁻⁵ to 1×10⁻² mol per mol of silver.

Reducing Agent

The thermographic recording element of the invention contains a reducingagent. In one embodiment of the invention, a compound of the followinggeneral formula (A) is contained as the reducing agent in thethermographic recording element.

Herein, R is hydrogen or alkyl groups having 1 to 10 carbon atoms suchas —C₄H₉ and 2,4,4-trimethylpentyl, R′ and R″ are alkyl groups having 1to 5 carbon atoms such as methyl, ethyl and n-butyl.

Illustrative, non-limiting examples of the compound of formula (A) aregiven below.

The compound of formula (A) is preferably used in an amount of 1×10⁻² to10 mol, more preferably 1×10⁻² to 1.5 mol per mol of silver.

In another embodiment of the invention, compounds of the followinggeneral formulae (R-I), (R-II), (R-III) and (R-IV) are contained as thereducing agent in the thermographic recording element.

In formula (R-III), Z forms a cyclic structure represented by thefollowing formula (Z-1) or (Z-2).

In formula (R-IV), Z forms a cyclic structure represented by thefollowing formula (Z-3) or (Z-4).

In formulae (R-I) and (R-II), each of L₁ and L₂ is a group —CH—(R₆)—,—CH—(R₆′)— or a sulfur atom, and n is a natural number.

Herein, R₁ to R₅, R₆, R₇ to R₁₀, R₁′ to R₅, R₆′, R¹¹ to R₁₃, R₁₁′ toR₁₃′, R₂₁ to R₂₆, R₂₁′ to R₂₄′ are hydrogen atoms, alkyl groups, arylgroups, aralkyl groups, halogen atoms, amino groups or substituentsrepresented by —OA, with the proviso that at least one of R¹ to R₅, atleast one of R₁′ to R₅′, and at least one of R₇ to R₁₀ each are a grouprepresented by —OA. In formula (R-II), L₁ is a sulfur atom where atleast one of R¹ to R₅ and at least one of R₁′ to R₅′ are groupsrepresented by —OA. Also, a plurality of substituents in each of R₁ toR₅, R₇ to R₁₀, R¹′ to R₅′, R₁₁ to R₁₃, R₁₁′ to R₁₃′, R₂₁ to R₂₆, R₂₁′ toR₂₄′, taken together, may form a ring.

A and A′ each are a hydrogen atom, alkyl group having 1 to 30 carbonatoms, acyl group having 1 to 30 carbon atoms, aryl group, phosphategroup or sulfonyl group.

R¹ to R₅, R₇ to R₁₀, R¹′ to R₅′, R¹¹ to R₁₃, R₁₁′ to R₁₃′, R₂₁ to R₂₆,R₂₁′ to R₂₄′, A and A′ may be substituted groups while typical examplesof the substituent include alkyl groups (including active methinegroups), nitro groups, alkenyl groups, alkynyl groups, aryl groups,heterocyclic ring-containing groups, groups containing a quaternizednitrogen atom-containing heterocyclic ring (e.g., pyridinio group),hydroxy groups, alkoxy groups (including groups containing recurringethyleneoxy or propyleneoxy units), aryloxy groups, acyloxy groups, acylgroups, alkoxycarbonyl groups, aryloxycarbonyl groups, carbamoyl groups,urethane groups, carboxyl groups, imido groups, amino groups,carbonamide groups, sulfonamide groups, ureido groups, thioureidogroups, sulfamoylamino groups, semicarbazide groups, thiosemicarbazidegroups, hydrazino-containing groups, quaternary ammonio-containinggroups, mercapto groups, (alkyl, aryl or heterocyclic) thio groups,(alkyl or aryl) sulfonyl groups, (alkyl or aryl) sulfinyl groups, sulfogroups, sulfamoyl groups, acylsulfamoyl groups, (alkyl or aryl)sulfonylureido groups, (alkyl or aryl) sulfonylcarbamoyl groups, halogenatoms, cyano groups, phosphoramide groups, phosphatestructure-containing groups, acylurea structure-bearing groups, seleniumor tellurium atom-containing groups, and tertiary or quaternarysulfonium structure-bearing groups. These substituents may be furthersubstituted, with preferred examples of the further substituent beingthe same as the foregoing substituents.

Illustrative, non-limiting, examples of the compounds represented byformulae (R-I), (R-II), (R-III) and (R-IV) are given below.

TABLE 23 No. R₁, R_(1′) R₂, R_(2′) R₃, R_(3′) R₄, R_(4′) R₅, R_(5′) L₁R₆ R-I-1 —OH —CH₃ —H —CH₃ —H S — R-I-2 —OH —CH₃ —H —C₂H₅ —H S — R-I-3—OH —CH₃ —H —C₄H₉ (t) —H S — R-I-4 —H —C₄H₉ (t) —OH —CPen —H CHR6 —HR-I-5 —H —C₄H₉ (t) —OH —C₄H₉ (t) —H CHR6 —TMB R-I-6 —H —C₄H₉ (t) —OH —H—H CHR6 —H R-I-7 —H —C₄H₉ (t) —OH —H —H CHR6 —C₃H₇ R-I-8 —H —CH₃ —OH—C₄H₉ (t) —H CHR6 —TMB R-I-9 —H —C₂H₅ —OH —C₄H₉ (t) —H CHR6 —H R-I-10 —H—CH₃ —OH —C₂H₅ —H CHR6 —TMB R-I-11 —H —CH₃ —OH —CH₃ —H S — R-I-12 —H—CH₃ —OH —CH₃ —Cl S — R-I-13 —H —CH₃ —OH —C₂H₅ —Cl S — R-I-14 —H —C₂H₅—OH —C₂H₅ —H S — R-I-15 —H —C₂H₅ —OH —CH₃ —Cl S — R-I-16 —H —CH₃ —OH—C₄H₉ (t) —H S — R-I-17 —H —CHex —OH —C₄H₉ (t) —H S —

TMB: 1,3,3-trimethylbutyl group

CPen: cyclopentyl group

CHex: cyclohexyl group

TABLE 24 No. R₁ R₂ R₃ R₄ R₅ R_(1′) R_(2′) R_(3′) R_(4′) R_(5′) L₁ R₆R-I-18 —OH —CH₃ —H —CH₃ —H —H —CH₃ —OH —CH₃ —H CH-R6 —H R-I-19 —OH—C₄H₉(t) —H —CH₃ —H —H —CH₃ —OH —CH₃ —H CH-R6 —H R-I-20 —OH —CH₃ —H —CH₃—H —H —CHex —OH —CH₃ —H CH-R6 —CH₃ R-I-21 —OH —C₄H₉(t) —H —CH₃ —H —H—CH₃ —OH —CH₃ —H CH-R6 —CH₃ R-I-22 —OH —CH₃ —H —CH₃ —H —H —CH₃ —OH —CH₃—H CH-R6 —TMB R-I-23 —OH —C₄H₉(t) —H —CH₃ —H —H —CH₃ —OH —CH₃ —H CH-R6—TMB R-I-24 —OH —CH₃ —H —CH₃ —H —H —CH₃ —OH —CH₃ —H S — R-I-25 —OH—C₄H₉(t) —H —CH₃ —H —H —CH₃ —OH —CH₃ —H S — R-I-26 —OH —CH₃ —H —CH₃ —H—H —CHex —OH —CH₃ —H S — R-I-27

R-I-28

TABLE 25 No R_(1′)R_(1′) R_(2′)R_(2′) R_(3′)R_(3′) R_(4′)R_(4′)R_(5′)R_(5′) R₇ R₈ R₉ R₁₀ L₁ R₆ L₂ R_(6′) n R-II-1 —OH —C₄H₉(t) —H —CH₃—H —OH —CH₃ —CH₃ —H CH-R6 —H CH-R6′ —CH₃ 1 R-II-2 —OH —CH₃ —H —CH₃ —H—OH —C₂H₅ —CH₃ —H CH-R6 —TMB CH-R6′ —CH₃ 1 R-II-3 —OH —C₄H₉(t) —H —CH₃—H —OH —CH₃ —CH₃ —H CH-R6 —H CH-R6′ —TMB 3 R-II-4 —OH —CH₃ —H —CH₃ —H—OH —C₂H₅ —CH₃ —H CH-R6 —TMB CH-R6′ —TMB 2 R-II-5 —H —C₄H₉(t) —OH —CH₃—H —OH —CH₃ —CH₃ —H S — CH-R6′ —CH₃ 1 R-II-6 —H —CH₃ —OH —CH₃ —H —OH—C₂H₅ —CH₃ —H S — S — 1 R-II-7 —H —C₄H₉(t) —OH —CH₃ —H —OH —CH₃ —CH₃ —HS — S — 2 R-II-8 —H —CH₃ —OH —CH₃ —H —OH —C₂H₅ —CH₃ —H S — CH-R6′ —TMB 3R-II-9

R-II-10

R-II-11

R-II-12

TABLE 26 No. Z R₁₁ R₁₂ R₁₃ R₂₁ R₂₂ R₂₃ R₂₄ R₂₅ R₂₆ A R-III-1 Z-1 —CH₃—CH₃ —CH₃ —H —H —H —H —CH₃ —C₁₆H₃₃ —H R-III-2 Z-1 —CH₃ —CH₃ —CH₃ —H —H—H —H —CH₃ —C₁₆H₁₃ —H R-III-3 Z-1 —CH₃ —C₈H₁₇ —H —H —CH₃ —H —H —CH₃ —CH₃—H R-III-4 Z-1 —H —C₈H₁₇ —H —H —CH₃ —H —H —CH₃ —CH₃ —H R-III-5 Z-1 —H —H—CH₃ —H —H —H —H —CH₃ —C₁₆H₃₃ —H R-III-6 Z-1 —H —CH₃ —H —CH₃ —CH₃ —H —H—CH₃ —CH₃ —H R-III-7 Z-1 —H —CH₃ —H —CH₃ —CH₃ —H —H —CH₃ —DHP —H DHP:2,4-dihydroxyphenyl group

TABLE 27 No. Z R₁₁, R_(11′) R₁₂, R_(12′) R₁₃, R_(13′) R₂₁, R₂₂ R_(21′),R_(22′) R₂₃, R₂₄ R_(23′), R_(24′) A R-III-8 Z-2 —H —CH₃ —H —CH₃ —CH₃ —H—H —H R-III-9 Z-2 —CH₃ —CH₃ —CH₃ —H —H —CH₃ —CH₃ —H R-III-10 Z-2 —CH₃—CH₃ —CH₃ —H —H —H —H —H R-III-11 Z-2 —CH₃ —OH —CH₃ —CH₃ —CH₃ —H —H —HR-III-12 Z-2 —H —OH —CH₃ —CH₃ —CH₃ —H —H —H

TABLE 28 No. Z R₁₁ R₁₂ R₁₃ R₂₁, R₂₂ R₂₃, R₂₄ R₂₅, R₂₆ A R-IV-1 Z-3 —H—OH —CH₃ —CH₃ —H —H —H R-IV-2 Z-3 —CH₃ —CH₃ —CH₃ —CH₃ —H —H —H

TABLE 29 No. Z R₁₁, R_(11′) R₁₂, R_(12′) R₁₃, R_(13′) R₂₁, R_(21′) R₂₂,R_(22′) R₂₃, R₂₄ R_(23′), R_(24′) A R-IV-3 Z-4 —CH₃ —H —H —CH₃ —CH₃ —H—H —H R-IV-4 Z-4 —CH₃ —CH₃ —H —CH₃ —CH₃ —H —H —H R-IV-5 Z-4 —CH₃ —H —H—C₂H₅ —CH₃ —H —H —H

The reducing agents represented by the general formulae (R-I) to (R-IV)are preferably used in amounts of 1×10⁻³ to 10 mol, more preferably1×10⁻² to 1.5 mol per mol of silver.

The compounds of formula (A) and the compounds of formulae (R-I) to(R-IV) may be used alone or in admixture. When they are used inadmixture, the auxiliary reducing agent and the main reducing agent arepreferably used in a molar ratio between 1/1000 and 1/1, more preferablybetween 1/100 and 1/1.

The thermographic recording element according to the invention isprocessed by a heat development process to form photographic images. Asdescribed in the preamble, photothermographic elements which constituteone embodiment of the invention are disclosed in U.S. Pat. Nos.3,152,904 and 3,457,075, D. Morgan and B. Shely, “Thermally ProcessedSilver Systems” in “Imaging Processes and Materials,” Neblette, 8th Ed.,Sturge, V. Walworth and A. Shepp Ed., page 2, 1969.

The thermographic recording element of the invention which formsphotographic images through heat development preferably contains areducible silver source (e.g., organic silver salt), a catalytic amountof a photocatalyst (e.g., silver halide), a toner for controlling thetone of silver, and a reducing agent, typically dispersed in a binder(typically organic binder) matrix. Although the photothermographicmaterial is stable at room temperature, it is developed merely byheating at an elevated temperature (e.g., 80° C. or higher) afterexposure, that is, without a need for a processing solution. Uponheating, redox reaction takes place between the reducible silver source(functioning as an oxidizing agent) and the reducing agent to formsilver. This redox reaction is promoted by the catalysis of a latentimage produced by exposure. Silver formed by reaction of the organicsilver salt in exposed regions provides black images in contrast tounexposed regions, forming an image.

The thermographic recording element of the invention has at least oneimage forming layer, typically a photo-sensitive layer, on a support. Itis acceptable to form only an image forming layer such as aphotosensitive layer on a support although it is preferred to form atleast one image protective layer such as a non-photosensitive layer onthe image forming layer such as the photosensitive layer.

In the photothermographic elements which constitute the preferredembodiment of the invention, in order to control the quantity orwavelength distribution of light transmitted to the photosensitivelayer, a filter layer may be formed on the same side as or on theopposite side to the photo-sensitive layer, or a dyestuff or pigment maybe contained in the photosensitive layer. The dyestuff used to this endis preferably selected from the compounds described in Japanese PatentApplication No. 11184/1995.

The photosensitive layer serving as the image forming layer may consistof two or more strata. Also a combination of high/low sensitivity strataor low/high sensitivity strata may be used for the adjustment ofgradation.

Various additives may be added to any of the image forming layer(typically photosensitive layer), non-image-forming layer (typicallynon-photosensitive layer), and other layers.

In the thermographic recording element of the invention, variousadditives such as surfactants, antioxidants, stabilizers, plasticizers,UV absorbers, and coating aids may be used.

Binder

A binder is used to hold such additives. It is preferably transparent orsemi-transparent and generally colorless. Exemplary binders arenaturally occurring polymers, synthetic resins, polymers and copolymers,and other film-forming media, for example, gelatin, gum arabic,poly(vinyl alcohol), hydroxyethyl cellulose, cellulose acetate,cellulose acetate butyrate, polylvinyl pyrrolidone), casein, starch,poly(acrylic acid), poly(methyl methacrylate), polyvinyl chloride,poly(methacrylic acid), copoly(styrene-maleic anhydride),copoly(styrene-acrylonitrile), copoly(styrene-butadiene), poly(vinylacetals) (e.g., poly(vinyl formal) and poly(vinyl butyral)), polyesters,polyurethanes, phenoxy resins, poly(vinylidene chloride), polyepoxides,polycarbonates, poly(vinyl acetate), cellulose esters, and polyamides.The binder may be dispersed in water, organic solvent or emulsion toform a dispersion which is coated to form a layer.

At least one layer of the image-forming layers used herein may be animage forming layer wherein a polymer latex constitutes more than 50% byweight of the entire binder. This image forming layer is sometimesreferred to as “inventive image-forming layer” and the polymer latexused. as the binder therefor is referred to as “inventive polymerlatex,” hereinafter. The term “polymer latex” used herein is adispersion of a microparticulate water-insoluble hydrophobic polymer ina water-soluble dispersing medium. With respect to the dispersed state,a polymer emulsified in a dispersing medium, an emulsion polymerizedpolymer, a micelle dispersion, and a polymer having a hydrophilicstructure in a part of its molecule so that the molecular chain itselfis dispersed on a molecular basis are included. With respect to thepolymer latex, reference is made to Okuda and Inagaki Ed., “SyntheticResin Emulsion,” Kobunshi Kankokai, 1978; Sugimura, Kataoka, Suzuki andKasahara Ed., “Application of Synthetic Latex,” Kobunshi Kankokai, 1993;and Muroi, “Chemistry of Synthetic Latex,” Kobunshi Kankokai, 1970.Dispersed particles should preferably have a mean particle size of about1 to 50,000 nm, more preferably about 5 to 1,000 nm. No particular limitis imposed on the particle size distribution of dispersed particles, andthe dispersion may have either a wide particle size distribution or amonodisperse particle size distribution.

The inventive polymer latex used herein may be either a latex of theconventional uniform structure or a latex of the so-called core/shelltype. In the latter case, better results are sometimes obtained when thecore and the shell have different glass transition temperatures.

The inventive polymer latex should preferably have a minimumfilm-forming temperature (MFT) of about −30° C. to 90° C., morepreferably about 0° C. to 70° C. A film-forming aid may be added inorder to control the minimum film-forming temperature. The film-formingaid is also referred to as a plasticizer and includes organic compounds(typically organic solvents) for lowering the minimum film-formingtemperature of a polymer latex. It is described in Muroi, “Chemistry ofSynthetic Latex,” Kobunshi Kankokai, 1970.

Polymers used in the inventive polymer latex according to the inventioninclude acrylic resins, vinyl acetate resins, polyester resins,polyurethane resins, rubbery resins, vinyl chloride resins, vinylidenechloride resins, polyolefin resins, and copolymers thereof. The polymermay be linear or branched or crosslinked. The polymer may be either ahomopolymer or a copolymer having two or more monomers polymerizedtogether. The copolymer may be either a random copolymer or a blockcopolymer. The polymer preferably has a number average molecule weightMn of about 5,000 to about 1,000,000, more preferably about 10,000 toabout 100,000. Polymers with a too lower molecular weight wouldgenerally provide a low film strength after coating whereas polymerswith a too higher molecular weight are difficult to form films.

The polymer of the inventive polymer latex should preferably have anequilibrium moisture content at 25° C. and RH 60% of up to 2% by weight,more preferably up to 1% by weight. The lower limit of equilibriummoisture content is not critical although it is preferably 0.01% byweight, more preferably 0.03% by weight. With respect to the definitionand measurement of equilibrium moisture content, reference should bemade to “Polymer Engineering Series No. 14, Polymer Material TestMethods,” Edited by Japanese Polymer Society, Chijin Shokan PublishingK.K., for example.

Illustrative examples of the polymer latex which can be used as thebinder in the image-forming layer of the thermo-graphic image recordingelement of the invention include latices of methyl methacrylate/ethylacrylate/methacrylic acid copolymers, latices of methylmethacrylate/2-ethylhexyl acrylate/styrene/acrylic acid copolymers,latices of styrene/butadiene/acrylic acid copolymers, latices ofstyrene/butadiene/divinyl benzene/methacrylic acid copolymers, laticesof methyl methacrylate/vinyl chloride/acrylic acid copolymers, andlatices of vinylidene chloride/ethyl acrylate/acrylonitrile/methacrylicacid copolymers. These polymers or polymer latices are commerciallyavailable. Exemplary acrylic resins are Sebian A-4635, 46583 and 4601(Daicell Chemical Industry K.K.) and Nipol LX811, 814, 820, 821 and 857(Nippon Zeon K.K.). Exemplary polyester resins are FINETEX ES650, 611,675, and 850 (Dai-Nippon Ink Chemical K.K.) and WD-size and WMS (EastmanChemical Products, Inc.). Exemplary polyurethane resins are HYDRAN AP10,20, 30 and 40 (Dai-Nippon Ink Chemical K.K.). Exemplary rubbery resinsare LACSTAR 7310K, 3307B, 4700H and 7132C (Dai-Nippon Ink Chemical K.K.)and Nipol LX416, 410, 438C and 2507 (Nippon Zeon K.K.). Exemplary vinylchloride resins are G351 and G576 (Nippon Zeon K.K.). Exemplaryvinylidene chloride resins are L502 and L513 (Asahi Chemicals K.K.).Exemplary olefin resins are Chemipearl S120 and SA100 (MitsuiPetro-Chemical K.K.). These polymers may be used alone or in admixtureof two or more.

In the inventive image-forming layer, the polymer latex described aboveis preferably used in an amount of at least 50% by weight, especially atleast 70% by weight, of the entire binder. In the inventiveimage-forming layer, a hydrophilic polymer may be added in an amount ofless than 50% by weight of the entire binder. Such hydrophilic polymersare gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropylcellulose, carboxymethyl cellulose, and hydroxypropyl methyl cellulose.The amount of the hydrophilic polymer added is preferably less than 30%by weight of the entire binder in the image-forming layer.

The inventive image-forming layer is preferably formed by applying anaqueous coating solution followed by drying. By the term “aqueous”, itis meant that water accounts for at least 30% by weight of the solventor dispersing medium of the coating solution. The component other thanwater of the coating solution may be a water-miscible organic solventsuch as methyl alcohol, ethyl alcohol, isopropyl alcohol, methylcellosolve, ethyl cellosolve, dimethylformamide or ethyl acetate.Exemplary solvent compositions include water, a 90/10 or 70/30 mixtureof water/methanol, a 90/10 mixture of water/ethanol, a 90/10 mixture ofwater/isopropanol, a 95/5 mixture of water/dimethyl-formamide, a 80/15/5or 90/5/5 mixture of water/methanol/dimethylformamide, all expressed ina weight ratio. The method described in U.S. Pat. No. 5,496,695 is alsouseful.

In the inventive image-forming layer, the total amount of binder ispreferably 0.2 to 30 g/m², more preferably 1 to 15 g/m² per layer. Tothe image forming layer, crosslinking agents for crosslinking,surfactants for ease of application, and other addenda may be added.

Addition of toners is quite desirable. Preferred toners are disclosed inResearch Disclosure No. 17029. Exemplary toners include imides such asphthalimide; cyclic imides such as succinimide, pyrazoline-5-ones,quinazolinone, 3-phenyl-2-pyrazoline-5-one, 1-phenylurazol, quinazolineand 2,4-thiazolizinedione; naphthalimides such asN-hydroxy-1,8-naphthalimide; cobalt complexes such as cobalt hexaminetrifluoroacetate; mercaptans such as 3-mercapto-1,2,4-triazole;N-(aminomethyl)aryldicarboxyimides such asN-(dimethylaminomethyl)phthalimide; combinations of a blocked pyrazole,an isothiuronium derivative and a certain optical bleaching agent suchas a combination ofN,N′-hexamethylenebis(1-carbamoyl-3,5-dimethylpyrazole),1,8-(3,6-dioxaoctane)bis(isothiuroniumtrifluoroacetate) and2-tribromomethylsulfonyl-benzothiazole; merocyanine dyes such as3-ethyl-5-{(3-ethyl-2-benzothiazolinylidene)-1-methylethylidene}-2-thio-2,4-oxazolidinedione;phthalazinones, phthalazinone derivatives or metal salts thereof such as4-(1-naphthyl)phthalazinone, 6-chloro-phthalazinone,5,7-dimethyloxyphthalazinone and 2,3-dihydro-1,4-phthalazinedione;combinations of phthalazinones with sulfinic acid derivatives such as acombination of 6-chlorophthalazinone with sodium benzenesulfinate and acombination of 8-methylphthalazinone with sodium p-trisulfonate;combinations of phthalazines with phthalic acid; combinations ofphthalazines (inclusive of phthalazine adducts) with maleic anhydrideand at least one of phthalic acid, 2,3-naphthalenedicarboxylic acid ando-phenylenic acid derivative and anhydrides thereof (e.g., phthalicacid, 4-methylphthalic acid, 4-nitrophthalic acid, andtetrachloro-phthalic anhydride); quinazolinediones, benzoxazine, andnaphthoxazine derivatives; benzoxazine-2,4-diones such as1,3-benzoxazine-2,4-dione; pyrimidine and asym-triazines such as2,4-dihydroxypyrimidine; and tetraazapentalene derivatives such as3,6-dimercapto-1,4-diphenyl-1H,4H-2,3a,5,6a-tetraazapentalene.Phthalazones are preferred toners.

The silver halide which is useful as a catalytic amount of photocatalystin the photothermographic element according to the preferred embodimentof the invention may be selected from photosensitive silver halides suchas silver bromide, silver iodide, silver chloride, silver chlorobromide,silver iodobromide, and silver chloroiodobromide, with an iodide ionbeing preferably contained. The silver halide may be added to the imageforming layer by any desired method whereupon the silver halide isdisposed close to the reducible silver source. In general, the silverhalide is preferably contained in an amount of 0.75 to 30% by weightbased on the reducible silver source. The silver halide may be preparedby converting a silver soap moiety through reaction with a halide ion,or by preforming silver halide and adding it upon generation of a soap,or a combination of these methods. The latter method is preferred.

The reducible silver source is preferably selected from silver salts oforganic and hetero-organic acids containing a reducible silver ionsource, especially silver salts of long chain aliphatic carboxylic acidshaving 10 to 30 carbon atoms, especially 15 to 25 carbon atoms. Alsopreferred are complexes of organic or inorganic silver salts withligands having an overall stability constant to silver ion in the rangeof 4.0 to 10.0. Preferred examples of the silver salt are described inResearch Disclosure Nos. 17029 and 29963. Included are silver salts oforganic acids (e.g., gallic acid, oxalic acid, behenic acid, stearicacid, palmitic acid, and lauric acid); silver salts ofcarboxyalkylthio-ureas (e.g., 1-(3-carboxypropyl)thiourea and1-(3-carboxy-propyl)-3,3-dimethylthiourea); silver complexes ofpolymeric reaction products of aldehydes and hydroxy-substitutedaromatic carboxylic acids (exemplary aldehydes are formaldehyde,acetaldehyde and butylaldehyde and exemplary hydroxy-substituted acidsare salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, and5,5-thiodisalicylic acid); silver salts or complexes of thioenes (e.g.,3-(2-carboxy-ethyl)-4-hydroxymethyl-4-(thiazoline-2-thioene and3-carboxymethyl-4-thiazoline-2-thioene); silver complexes or salts ofnitrogenous acids such as imidazoles, pyrazoles, urazoles,1,2,4-thiazoles, 1H-tetrazoles, 3-amino-5-benzyl-thio-1,2,4-triazoles,and benzotriazoles; silver salts of saccharin and5-chlorosalicylaldoxime; and silver salts of mercaptides. The preferredsilver source is silver behenate. The reducible silver source ispreferably used in an amount of up to 3 g/m², more preferably up to 2g/m² of silver. The lower limit is usually 0.1 g/m², though notcritical.

An antifoggant may be contained in the thermographic recording elementaccording to the invention. The most effective antifoggant was mercuryion. Use of a mercury compound as the antifoggant in photosensitivematerial is disclosed, for example, in U.S. Pat. No. 3,589,903. Mercurycompounds, however, are undesirable from the ecological aspect.Preferred in this regard are non-mercury antifoggants as disclosed, forexample, in U.S. Pat. Nos. 4,546,075 and 4,452,885 and JP-A 57234/1984.

Especially preferred non-mercury antifoggants are compounds as disclosedin U.S. Pat. Nos. 3,874,946 and 4,756,999 and heterocyclic compoundshaving at least one substituent represented by —C(X¹) (X²) (X³) whereinX¹ and X² are halogen atoms such as F, Cl, Br, and I, and X³ is hydrogenor halogen. Preferred examples of the antifoggant are shown below.

More preferred antifoggants are disclosed in U.S. Pat. No. 5,028,523,British Patent Application Nos. 92221383.4, 9300147.7 and 9311790.1.

In the photothermographic material according to the preferred embodimentof the invention, there may be used sensitizing dyes as disclosed inJP-A 159841/1988, 140335/1985, 231437/1988, 259651/1988, 304242/1988,and 15245/1988, U.S. Pat. Nos. 4,639,414, 4,740,455, 4,741,966,4,751,175, and 4,835,096.

Useful sensitizing dyes which can be used herein are described inResearch Disclosure, Item 17643 IV-A (December 1978, page 23), ibid.,Item 1831 X (August 1978, page 437) and the references cited therein.

It is advantageous to select a sensitizing dye having appropriatespectral sensitivity to the spectral properties of a particular lightsource of various scanners. Exemplary sensitizing dyes include (A)simple merocyanines as described in JP-A 162247/1985 and 48653/1990,U.S. Pat. No. 2,161,331, W. German Patent No. 936,071, and JapanesePatent Application No. 189532/1991 for argon laser light sources; (B)tri-nucleus cyanine dyes as described in JP-A 62425/1975, 18726/1979 and102229/1984 and merocyanines as described in Japanese Patent ApplicationNo. 103272/1994 for He—Ne laser light sources; (C) thiacarbocyanines asdescribed in JP-B 42172/1973, 9609/1976, 39818/1980, JP-A 284343/1987and 105135/1990 for LED light sources and red semiconductor laser lightsources; and (D) tricarbocyanines as described in JP-A 191032/1984 and80841/1985 and 4-quinoline nucleus-containing dicarbocyanines asdescribed in JP-A 192242/1984 and 67242/1991 (as represented by formulae(IIIa) and (IIIb) therein) for infrared semiconductor laser lightsources.

These sensitizing dyes may be used alone or in admixture of two or more.A combination of sensitizing dyes is often used for the purpose ofsupersensitization. In addition to the sensitizing dye, the emulsion maycontain a dye which itself has no spectral sensitization function or acompound which does not substantially absorb visible light, but iscapable of supersensitization.

For exposure of the photothermographic material of the invention, an Arlaser (488 nm), He—Ne laser (633 nm), red semiconductor laser (670 nm),and infrared semiconductor laser (780 nm and 830 nm) are preferablyused.

A dyestuff-containing layer may be included as an anti-halation layer inthe photothermographic material of the invention. For Ar laser, He—Nelaser, and red semiconductor laser light sources, a dyestuff ispreferably added so as to provide an absorbance of at least 0.3, morepreferably at least 0.8 at an exposure wavelength in the range of 400 to750 nm. For infrared semiconductor laser light sources, a dyestuff ispreferably added so as to provide an absorbance of at least 0.3, morepreferably at least 0.8 at an exposure wavelength in the range of 750 to1500 nm. The dyestuffs may be used alone or in admixture of two or more.The dyestuff may be added to a dyestuff layer disposed on the same sideas the photosensitive layer adjacent to the support or a dyestuff layerdisposed on the support opposite to the photosensitive layer.

Various supports are used in the invention. Useful supports are paper,synthetic paper, synthetic resin-laminated paper (exemplary syntheticresins being polyethylene, polypropylene and polystyrene), plastic films(e.g., polyethylene terephthalate, polycarbonate, polyimide, nylon, andcellulose triacetate), metal sheets (e.g., aluminum, aluminum alloys,zinc, iron and copper), paper sheets and plastic films having suchmetals laminated or evaporated thereon.

When plastic film is passed through a thermographic processor, the filmexperiences dimensional shrinkage or expansion. When the thermographicrecording element is intended for printing purposes, this dimensionalshrinkage or expansion gives rise to a serious problem against precisionmulti-color printing. Therefore, the invention favors the use of a filmexperiencing a minimal dimensional change. Exemplary materials arestyrene polymers having a syndiotactic structure and heat-treatedpolyethylene. Also useful are materials having a high glass transitiontemperature, for example, polyether ethyl ketone, poly-styrene,polysulfone, polyether sulfone, and polyarylate.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation.

The trade names used in Examples have the following meaning.

Denka Butyral: polyvinyl butyral by Denki Kagaku Kogyo K.X.

CAB 171-15S: cellulose acetate butyrate by Eastman Chemical Products,Inc.

Sildex: spherical silica by Dokai Chemical K.K.

Sumidur N3500: polyisocyanate by Sumitomo-Bayern Urethane K.K.

Megafax F-176P: fluorinated surfactant by Dai-Nippon Ink Chemicals K.K.

LACSTAR 3307B: styrene-butadiene rubber (SBR) latex by Dai-Nippon InkChemicals K.K. The polymer has an equilibrium moisture content of 0.6 wt% at 25° C. and RH 60% and the dispersed particles have a mean particlediameter of about 0.1 to 0.15 μm.

Example 1 Organic Silver Salt Emulsion A

To 12 liters of water were added 840 grams of behenic acid and 95 gramsof stearic acid. To the solution kept at 90° C., a solution of 48 gramsof sodium hydroxide and 63 grams of sodium carbonate in 1.5 liters ofwater was added. The solution was stirred for 30 minutes and then cooledto 50° C. whereupon 1.1 liters of a 1% aqueous solution ofN-bromosuccinimide (C-12) was added. With stirring, 2.3 liters of a 17%aqueous solution of silver nitrate was slowly added. While the solutionwas kept at 35° C., with stirring, 1.5 liters of a 2% aqueous solutionof potassium bromide was added over 2 minutes. The solution was stirredfor 30 minutes whereupon 2.4 liters of a 1% aqueous solution ofN-bromosuccinimide was added. With stirring, 3,300 grams of a solutioncontaining 1.2% by weight of polyvinyl acetate in butyl acetate wasadded to the aqueous mixture. The mixture was allowed to stand for 10minutes, separating into two layers. After the aqueous layer wasremoved, the remaining gel was washed twice with water. There wasobtained a gel-like mixture of silver behenate/stearate and silverbromide, which was dispersed in 1,800 grams of a 2.6% 2-butanonesolution of polyvinyl butyral (Denka Butyral #3000-K). The dispersionwas further dispersed in 600grams of polyvinyl butyral (Denka Butyral#4000-2) and 300 grams of isopropyl alcohol, obtaining an organic acidsilver salt emulsion of needle grains having a mean minor diameter of0.05 μm, a mean major diameter of 1.2 μm, and a coefficient of variationof 25%.

Emulsion Layer Coating Solution A

The following chemicals were added to the above-prepared organic acidsilver salt emulsion A in amounts per mol of silver. With stirring at25° C., 10 mg of sodium phenylthiosulfonate, 20 mg of Sensitizing Dye A,25 mg of Sensitizing Dye B, 15 mg of Sensitizing Dye C, 2 grams of2-mercapto-5-methylbenzimidazole (C-1), 1 gram of2-mercapto-5-methylbenzothiazole (C-2), 21.5 grams of4-chlorobenzophenone-2-carboxylic acid (C-3), 580 grams of 2-butanoneand 220 grams of dimethylformamide were added to the emulsion, which wasallowed to stand for 3 hours. With stirring, 4.5 grams of4,6-ditrichloromethyl-2-phenyltriazine (C-4), 2 grams of Disulfidecompound A, 160 grams of1,1-bis(2-hydroxy-3,5-dimethylphenyl)-3,5,5-trimethylhexane (C-5), 15grams of phthalazine (C-6), 5 grams of tetrachlorophthalic acid (C-7),an amount of a hydrazine derivative as shown in Table 30, an amount of acompound of formula (1) to (14) or a comparative compound as shown inTable 30, 1.1 grams of fluorinated surfactant Megafax F-176P, 590 gramsof 2-butanone, and 10 grams of methyl isobutyl ketone were added to theemulsion.

Emulsion Surface Protective Layer Coating Solution A

A coating solution A for an emulsion layer surface protective layer wasprepared by dissolving 75 grams of cellulose acetate butyrate CAB171-15S, 5.7 grams of 4-methylphthalic acid (C-8), 1.5 grams oftetrachlorophthalic anhydride (C-9), 10 grams of2-tribromomethylsulfonyl-benzothiazole (C-10), 2 grams of phthalazone(C-11), 0.3 gram of Megafax F-176P, 2 grams of spherical silica SildexH31 (mean size 3 μm), and 5 grams of polyisocyanate Sumidur N3500 in3070 grams of 2-butanone and 30 grams of ethyl acetate.

Preparation of Coated Sample

A back layer coating solution was prepared by adding 6 grams ofpolyvinyl butyral Denka Butyral #4000-2, 0.2 gram of spherical silicaSildex H121 (mean size 12 μm), 0.2 gram of spherical silica Sildex H51(mean size 5 μm), and 0.1 gram of Megafax F-176P to 64 grams of2-propanol and mixing them into a solution. Further, a mixed solution of420 mg of Dyestuff A in 10 grams of methanol and 20 grams of acetone anda solution of 0.8 gram of 3-isocyanatomethyl-3,5,5-trimethylhexylisocyanate in 6 grams of ethyl acetate were added to the solution.

A polyethylene terephthalate film having a moisture-proof undercoat ofvinylidene chloride on either surface was coated on one surface with theback surface coating solution so as to give an optical density of 0.7 at633 nm.

On the thus prepared support, the emulsion layer coating solution wascoated so as to give a coverage of 2 g/m² of silver, and the emulsionlayer protective layer coating solution was then coated on the emulsionlayer so as to give a dry thickness of 5 μm, obtaining a coated sample.

Some of the compounds used in this Example are shown below by structuralformulae. They are also used in Examples 2 and 7. For the sake ofconvenience, the structural formulae of compounds used in Examples 2 and7 are also shown here.

Photographic Property Test

The recording element samples prepared above were exposed by means of ahelium-neon light source color scanner SG-608 (by Dai-Nippon ScreenK.K.) and heated for development at 115° C. for 25 seconds on a heatdrum. They were further exposed to a halogen lamp for 15 seconds. Theresulting images were determined for Dmax and sensitivity by adensitometer. The sensitivity (S) is the reciprocal of a ratio of theexposure providing a density of Dmin +1.5. The gradient of a straightline connecting points of density 0.3 and 3.0 on a characteristic curveis also reported as gradation (γ). The results are shown in Table 30.

Black Pepper Rating

The unexposed recording element samples were heated for development at120° C. for 60 seconds on a heat drum. By visually observing the numberof black peppers generated, the samples were rated on a 5-point scalewith “5” for best quality and “1” for worst quality. Rating “3” is thepractically acceptable limit, and samples rated “2” and “1” areunacceptable. The results are shown in Table 30.

TABLE 30 Addition Addition amount Substituted amount Hydrazine (mol/molalkene (mol/mol black compound of Ag) derivative of Ag) Dmax S γ pepper 1* — — — — 2.6 0.80 — 5  2* 1a 2.4 × 10⁻³ — — 3.4 1.16 12.1 2  3* 54a2.0 × 10⁻³ — — 3.8 1.30 13.6 3  4* 56a 1.8 × 10⁻³ — — 3.8 1.30 13.6 3 5* 56m 7.2 × 10⁻³ — — 3.6 1.23 12.9 2  6* 58a 1.4 × 10⁻³ — — 3.9 1.3313.9 3  7* 66a 8.0 × 10⁻³ — — 3.5 1.20 12.5 2  8* 95-1 6.0 × 10⁻³ — —3.7 1.27 13.2 2  9* 104x 1.8 × 10⁻³ — — 3.5 1.20 12.5 2 10* 106-10 9.0 ×10⁻³ — — 3.6 1.23 12.9 2 11* 118 9.5 × 10⁻³ — — 3.4 1.16 12.1 2 12* 1a2.4 × 10⁻³ VC-1 1.9 × 10⁻³ 3.6 1.22 12.3 2 13* 54a 2.0 × 10⁻³ VC-1 1.6 ×10⁻³ 4.0 1.37 14.3 3 14* 56a 1.8 × 10⁻³ VC-1 1.4 × 10⁻³ 4.0 1.37 14.3 315* 56m 7.2 × 10⁻³ VC-1 5.8 × 10⁻³ 3.8 1.29 13.5 3 16* 58a 1.4 × 10⁻³VC-1 1.1 × 10⁻³ 4.1 1.40 14.6 3 17* 66a 8.0 × 10⁻³ VC-1 6.4 × 10⁻³ 3.71.26 13.1 2 18* 95-1 6.0 × 10⁻³ VC-1 4.8 × 10⁻³ 3.9 1.33 13.9 3 19* 104x1.8 × 10⁻³ VC-1 1.4 × 10⁻³ 3.7 1.26 13.1 2 20* 106-10 9.0 × 10⁻³ VC-17.2 × 10⁻³ 3.8 1.29 13.5 3 21* 118 9.5 × 10⁻³ VC-1 7.6 × 10⁻³ 3.6 1.2212.8 2 22** 1a 2.4 × 10⁻³ 1 1.7 × 10⁻³ 4.1 1.40 14.6 4 23** 54a 2.0 ×10⁻³ 1 1.4 × 10⁻³ 4.6 1.56 16.3 5 24** 56a 1.8 × 10⁻³ 1 1.3 × 10⁻³ 4.61.56 16.3 5 25** 56m 7.2 × 10⁻³ 1 5.0 × 10⁻³ 4.3 1.48 15.4 5 26** 58a1.4 × 10⁻³ 1 1.0 × 10⁻³ 4.7 1.60 16.7 5 27** 66a 8.0 × 10⁻³ 1 5.6 × 10⁻³4.2 1.44 15.0 4 28** 95-1 6.0 × 10⁻³ 1 4.2 × 10⁻³ 4.4 1.52 15.9 5 29**104x 1.8 × 10⁻³ 1 1.3 × 10⁻³ 4.2 1.44 15.0 4 30** 106-10 9.0 × 10⁻³ 16.3 × 10⁻³ 4.3 1.48 15.4 5 31** 118 9.5 × 10⁻³ 1 6.7 × 10⁻³ 4.1 1.4014.6 4 32** 1a 2.4 × 10⁻³ 63 1.7 × 10⁻³ 4.1 1.39 14.5 4 33** 54a 2.0 ×10⁻³ 63 1.4 × 10⁻³ 4.5 1.55 16.2 5 34** 56a 1.8 × 10⁻³ 63 1.3 × 10⁻³ 4.51.55 16.2 5 35** 56m 7.2 × 10⁻³ 63 5.2 × 10⁻³ 4.3 1.47 15.4 5 36** 58a1.4 × 10⁻³ 63 1.0 × 10⁻³ 4.7 1.59 16.6 5 37** 66a 8.0 × 10⁻³ 63 5.8 ×10⁻³ 4.2 1.43 14.9 4 38** 95-1 6.0 × 10⁻³ 63 4.3 × 10⁻³ 4.4 1.51 15.3 539** 104x 1.8 × 10⁻³ 63 1.3 × 10⁻³ 4.2 1.43 14.9 4 40** 106-10 9.0 ×10⁻³ 63 6.5 × 10⁻³ 4.3 1.47 15.4 5 41** 118 9.5 × 10⁻³ 63 6.8 × 10⁻³ 4.11.39 14.5 4 42** 1a 2.4 × 10⁻³ 7 1.6 × 10⁻³ 4.0 1.38 14.4 4 43** 54a 2.0× 10⁻³ 7 1.4 × 10⁻³ 4.5 1.54 16.1 5 44** 56a 1.8 × 10⁻³ 7 1.2 × 10⁻³ 4.51.54 16.1 5 45** 56m 7.2 × 10⁻³ 7 4.9 × 10⁻³ 4.3 1.46 15.2 4 46** 58a1.4 × 10⁻³ 7 1.0 × 10⁻³ 4.6 1.58 16.5 5 47** 66a 8.0 × 10⁻³ 7 5.4 × 10⁻³4.1 1.42 14.8 4 48** 95-1 6.0 × 10⁻³ 7 4.1 × 10⁻³ 4.4 1.50 15.7 5 49**104x 1.8 × 10⁻³ 7 1.2 × 10⁻³ 4.1 1.42 14.8 4 50** 106-10 9.0 × 10⁻³ 76.1 × 10⁻³ 4.3 1.46 15.2 4 51** 118 9.5 × 10⁻³ 7 6.5 × 10⁻³ 4.0 1.3814.4 4 52** 1a 2.4 × 10⁻³ 14 1.7 × 10⁻³ 4.0 1.37 14.6 4 53** 54a 2.0 ×10⁻³ 14 1.4 × 10⁻³ 4.6 1.56 16.0 5 54** 56a 1.8 × 10⁻³ 14 1.3 × 10⁻³ 4.61.53 16.0 5 55** 56m 7.2 × 10⁻³ 14 5.2 × 10⁻³ 4.2 1.45 15.1 4 56** 58a1.4 × 10⁻³ 14 1.0 × 10⁻³ 4.6 1.57 16.4 5 57** 66a 8.0 × 10⁻³ 14 5.8 ×10⁻³ 4.1 1.41 14.7 4 58** 95-1 6.0 × 10⁻³ 14 4.3 × 10⁻³ 4.4 1.49 15.6 559** 104x 1.8 × 10⁻³ 14 1.3 × 10⁻³ 4.1 1.41 14.7 4 60** 106-10 9.0 ×10⁻³ 14 6.5 × 10⁻³ 4.2 1.45 15.1 4 61** 118 9.5 × 10⁻³ 14 6.8 × 10⁻³ 4.01.37 14.3 4 62** 1a 2.4 × 10⁻³ 37 1.6 × 10⁻³ 4.0 1.38 14.4 4 63** 54a2.0 × 10⁻³ 37 1.4 × 10⁻³ 4.5 1.55 16.1 5 64** 56a 1.8 × 10⁻³ 37 1.2 ×10⁻³ 4.5 1.55 16.1 5 65** 56m 7.2 × 10⁻³ 37 4.9 × 10⁻³ 4.3 1.46 15.3 466** 58a 1.4 × 10⁻³ 37 1.0 × 10⁻³ 4.6 1.59 16.6 5 67** 66a 8.0 × 10⁻³ 375.4 × 10⁻³ 4.2 1.42 14.9 4 68** 95-1 6.0 × 10⁻³ 37 4.1 × 10⁻³ 4.4 1.5115.7 5 69** 104x 1.8 × 10⁻³ 37 1.2 × 10⁻³ 4.2 1.42 14.9 4 70** 106-109.0 × 10⁻³ 37 6.1 × 10⁻³ 4.3 1.46 15.3 4 71** 118 9.5 × 10⁻³ 37 6.5 ×10⁻³ 4.0 1.38 14.4 4 72** 1a 2.4 × 10⁻³ 39 1.9 × 10⁻³ 4.1 1.39 14.5 473** 54a 2.0 × 10⁻³ 39 1.6 × 10⁻³ 4.5 1.55 16.2 5 74** 56a 1.8 × 10⁻³ 391.4 × 10⁻³ 4.5 1.55 16.2 5 75** 56m 7.2 × 10⁻³ 39 5.6 × 10⁻³ 4.3 1.4715.4 5 76** 58a 1.4 × 10⁻³ 39 1.1 × 10⁻³ 4.7 1.60 16.7 5 77** 66a 8.0 ×10⁻³ 39 6.2 × 10⁻³ 4.2 1.43 15.0 4 78** 95-1 6.0 × 10⁻³ 39 4.7 × 10⁻³4.4 1.51 15.8 5 79** 104x 1.8 × 10⁻³ 39 1.4 × 10⁻³ 4.2 1.43 15.0 4 80**106-10 9.0 × 10⁻³ 39 7.0 × 10⁻³ 4.3 1.47 15.4 5 81** 118 9.5 × 10⁻³ 397.4 × 10⁻³ 4.1 1.39 14.5 4 82** 1a 2.4 × 10⁻³ 41 1.8 × 10⁻³ 4.0 1.3814.4 4 83** 54a 2.0 × 10⁻³ 41 1.5 × 10⁻³ 4.5 1.55 16.1 5 84** 56a 1.8 ×10⁻³ 41 1.3 × 10⁻³ 4.5 1.55 16.1 5 85** 56m 7.2 × 10⁻³ 41 5.3 × 10⁻³ 4.31.46 15.3 4 86** 58a 1.4 × 10⁻³ 41 1.0 × 10⁻³ 4.6 1.59 16.6 5 87** 66a8.0 × 10⁻³ 41 5.9 × 10⁻³ 4.2 1.42 14.9 4 88** 95-1 6.0 × 10⁻³ 41 4.4 ×10⁻³ 4.4 1.51 15.7 5 89** 104x 1.8 × 10⁻³ 41 1.3 × 10⁻³ 4.2 1.42 14.9 490** 106-10 9.0 × 10⁻³ 41 6.7 × 10⁻³ 4.3 1.46 15.3 4 91** 118 9.5 × 10⁻³41 7.0 × 10⁻³ 4.0 1.38 14.4 4 *comparison **invention

It is evident from Table 30 that using hydrazine derivatives within thescope of the invention and compounds of formulae (1) to (14),thermographic recording elements satisfying all the requirements of highDmax, high contrast, and minimal black pepper are obtained.

Example 2 Silver Halide Grains B

In 900 ml of water were dissolved 7.5 grams of inert gelatin and 10 mgof potassium bromide. The solution was adjusted to pH 3.0 at atemperature of 35° C. To the solution, 370 ml of an aqueous solutioncontaining 74 grams of silver nitrate and an aqueous solution containingpotassium bromide and potassium iodide in a molar ratio of 94:6 andK₃[IrCl₆] were added over 10 minutes by the controlled double jet methodwhile maintaining the solution at pAg 7.7. Note that [IrCl₆]³⁻ was addedin an amount of 3×10⁻⁷ mol/mol of silver. Thereafter, 0.3 gram of4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene was added to the solution,which was adjusted to pH 5 with NaOH. There were obtained cubic silveriodobromide grains B having a mean grain size of 0.06 μm, a coefficientof variation of projected area of 8%, and a {100} face ratio of 87%. Theemulsion was desalted by adding a gelatin flocculant thereto to causeflocculation and sedimentation and then adjusted to pH 5.9 and pAg 7.5by adding 0.1 gram of phenoxyethanol.

Organic Acid Silver Emulsion B

A mixture of 10.6 grams of behenic acid and 300 ml of distilled waterwas mixed for 15 minutes at 90° C. With vigorous stirring, 31.1 ml of 1Nsodium hydroxide was added over 15 minutes to the solution, which wasallowed to stand at the temperature for one hour. The solution was thencooled to 30° C., 7 ml of 1N phosphoric acid was added thereto, and withmore vigorous stirring, 0.13 gram of N-bromosuccinimide (C-12) wasadded. Thereafter, with stirring, the above-prepared silver halidegrains B were added to the solution in such an amount as to give 2.5mmol of silver halide. Further, 25 ml of 1N silver nitrate aqueoussolution was continuously added over 2 minutes, with stirring continuedfor a further 90 minutes. With stirring, 37 grams of a 1.2 wt % butylacetate solution of polyvinyl acetate was slowly added to the aqueousmixture to form flocs in the dispersion. Water was removed, and waterwashing and water removal were repeated twice. With stirring, 20 gramsof a solution of 2.5% by weight polyvinyl butyral (Denka Butyral#3000-K) in a ½ solvent mixture of butyl acetate and isopropyl alcoholwas added. To the thus obtained gel-like mixture of organic acid silverand silver halide, 7.8 grams of polyvinyl butyral (Denka Butyral#4000-2) and 57 grams of 2-butanone were added. The mixture wasdispersed by a homogenizer, obtaining a silver behenate emulsion B ofneedle grains having a mean minor diameter of 0.04 μm, a mean majordiameter of 1 μm and a coefficient of variation of 30%.

Emulsion Layer Coating Solution B

The following chemicals were added to the above-prepared organic acidsilver salt emulsion B in amounts per mol of silver. With stirring at25° C., 10 mg of sodium phenylthiosulfonate, 25 mg of Sensitizing Dye A,20 mg of Sensitizing Dye B, 18 mg of Sensitizing Dye C, 2 grams of2-mercapto-5-methylbenzimidazole (C-1), 21.5 grams of4-chlorobenzophenone-2-carboxylic acid (C-3), 580 grams of 2-butanoneand 220 grams of dimethylformamide were added to the emulsion, which wasallowed to stand for 3 hours. With stirring, 4 grams of4,6-ditrichloromethyl-2-phenyltriazine (C-4), 2 grams of Disulfidecompound A, 170 grams of1,1-bis(2-hydroxy-3,5-dimethylphenyl)-3,5,5-trimethylhexane (C-5), 15grams of phthalazine (C-6), 5 grams of tetrachloro-phthalic acid (C-7),an amount of a hydrazine derivative as shown in Table 31, 1.1 grams ofMegafax F-176P, 590 grams of 2-butanone, and 10 grams of methyl isobutylketone were added to the emulsion.

Emulsion Surface Protective Layer Coating Solution B

A coating solution B for an emulsion layer surface protective layer wasprepared by dissolving 75 grams of CAB 171-15S, 5.7 grams of4-methylphthalic acid (C-8), 1.5 grams of tetrachlorophthalic anhydride(C-9), 8 grams of 5-tribromomethylsulfonyl-2-methylthiadiazole (C-13), 6grams of 2-tribromomethylsulfonylbenzothiazole (C-10), 3 grams ofphthalazone (C-11), 0.3 gram of Megafax F-176P, an amount of a compoundof formula (1) to (14) or a comparative compound as shown in Table 31, 2grams of spherical silica Sildex H31 (mean size 3 μm), and 6 grams ofpolyisocyanate Sumidur N3500 in 3070 grams of 2-butanone and 30 grams ofethyl acetate.

Preparation of Coated Sample

A back layer coating solution was prepared by adding 6 grams ofpolyvinyl butyral Denka Butyral #4000-2, 0.2 gram of spherical silicaSildex H121 (mean size 12 μm), 0.2 gram of spherical silica Sildex H51(mean size 5 μm), and 0.1 gram of Megafax F-176P to 64 grams of2-propanol and mixing them into a solution. Further, a mixed solution of420 mg of Dyestuff A in 10 grams of methanol and 20 grams of acetone anda solution of 0.8 gram of 3-isocyanatomethyl-3,5,5-trimethylhexylisocyanate in 6 grams of ethyl acetate were added to the solution.

A polyethylene terephthalate film having a moisture-proof undercoat ofvinylidene chloride on either surface was coated on one surface with theback surface coating solution so as to give an optical density of 0.7 at688 nm.

On the thus prepared support, the emulsion layer coating solution wascoated so as to give a coverage of 2 g/m² of silver and the emulsionlayer protective layer coating solution was then coated on the emulsionlayer so as to give a dry thickness of 5 μm, obtaining a coated sampleof thermographic recording element.

Photographic Property/black Pepper Tests

The samples were determined for photographic properties and black pepperas in Example 1. The results are shown in Table 31.

TABLE 31 Addition Addition amount Substituted amount Hydrazine (mol/molalkene (mol/mol black compound of Ag) derivative of Ag) Dmax S γ pepper 1* — — — — 2.6 0.80 — 5  2* 2b 1.8 × 10⁻³ — — 3.5 1.20 12.5 2  3* 31a1.9 × 10⁻³ — — 3.9 1.33 13.9 3  4* 34a 1.6 × 10⁻³ — — 3.8 1.30 13.6 3 5* 54a 2.0 × 10⁻³ — — 3.7 1.27 13.2 2  6* 55r 6.0 × 10⁻³ — — 3.9 1.3313.9 3  7* 56a 1.8 × 10⁻³ — — 3.6 1.23 12.9 2  8* 72x 9.5 × 10⁻³ — — 3.71.27 13.2 2  9* 83 2.2 × 10⁻³ — — 3.6 1.23 12.9 2 10* 95-1 5.0 × 10⁻³ —— 3.6 1.23 12.9 2 11* 109m 9.8 × 10⁻³ — — 3.5 1.20 12.5 2 12* 2b 1.8 ×10⁻³ VC-2 1.6 × 10⁻³ 3.7 1.26 13.2 2 13* 31a 1.9 × 10⁻³ VC-2 1.7 × 10⁻³4.1 1.41 14.7 3 14* 34a 1.6 × 10⁻³ VC-2 1.4 × 10⁻³ 4.0 1.37 14.3 3 15*54a 2.0 × 10⁻³ VC-2 1.8 × 10⁻³ 3.9 1.34 13.9 3 16* 55r 6.0 × 10⁻³ VC-25.4 × 10⁻³ 4.1 1.41 14.7 3 17* 56a 1.8 × 10⁻³ VC-2 1.6 × 10⁻³ 3.8 1.3013.6 3 18* 72x 9.5 × 10⁻³ VC-2 8.6 × 10⁻³ 3.9 1.34 13.9 3 19* 83 2.2 ×10⁻³ VC-2 2.0 × 10⁻³ 3.8 1.30 13.6 3 20* 95-1 5.0 × 10⁻³ VC-2 4.5 × 10⁻³3.8 1.30 13.6 3 21* 109m 9.8 × 10⁻³ VC-2 8.8 × 10⁻³ 3.7 1.26 13.2 2 22**2b 1.8 × 10⁻³ 2 1.4 × 10⁻³ 4.2 1.42 14.9 4 23** 31a 1.9 × 10⁻³ 2 1.5 ×10⁻³ 4.6 1.59 16.6 5 24** 34a 1.6 × 10⁻³ 2 1.3 × 10⁻³ 4.5 1.55 16.2 525** 54a 2.0 × 10⁻³ 2 1.6 × 10⁻³ 4.4 1.51 15.7 5 26** 55r 6.0 × 10⁻³ 24.8 × 10⁻³ 4.6 1.59 16.6 5 27** 56a 1.8 × 10⁻³ 2 1.4 × 10⁻³ 4.3 1.4715.3 4 28** 72x 9.5 × 10⁻³ 2 7.6 × 10⁻³ 4.4 1.51 15.7 5 29** 83 2.2 ×10⁻³ 2 1.8 × 10⁻³ 4.3 1.47 15.3 4 30** 95-1 5.0 × 10⁻³ 2 4.0 × 10⁻³ 4.31.47 15.3 4 31** 109m 9.8 × 10⁻³ 2 7.8 × 10⁻³ 4.2 1.42 14.9 4 32** 2b1.8 × 10⁻³ 38 1.5 × 10⁻³ 4.2 1.43 15.0 4 33** 31a 1.9 × 10⁻³ 38 1.6 ×10⁻³ 4.7 1.60 16.7 5 34** 34a 1.6 × 10⁻³ 38 1.3 × 10⁻³ 4.6 1.56 16.3 535** 54a 2.0 × 10⁻³ 38 1.7 × 10⁻³ 4.4 1.52 15.8 5 36** 55r 6.0 × 10⁻³ 385.0 × 10⁻³ 4.7 1.60 16.7 5 37** 56a 1.8 × 10⁻³ 38 1.5 × 10⁻³ 4.3 1.4815.4 5 38** 72x 9.5 × 10⁻³ 38 8.0 × 10⁻³ 4.4 1.52 15.8 5 39** 83 2.2 ×10⁻³ 38 1.8 × 10⁻³ 4.3 1.48 15.4 5 40** 95-1 5.0 × 10⁻³ 38 4.2 × 10⁻³4.3 1.48 15.4 5 41** 109m 9.8 × 10⁻³ 38 8.2 × 10⁻³ 4.2 1.43 15.0 4 42**2b 1.8 × 10⁻³ 12 1.4 × 10⁻³ 4.2 1.42 14.9 4 43** 31a 1.9 × 10⁻³ 12 1.5 ×10⁻³ 4.6 1.59 16.6 5 44** 34a 1.6 × 10⁻³ 12 1.3 × 10⁻³ 4.5 1.55 16.2 545** 54a 2.0 × 10⁻³ 12 1.6 × 10⁻³ 4.4 1.51 15.7 5 46** 55r 6.0 × 10⁻³ 124.8 × 10⁻³ 4.6 1.59 16.6 5 47** 56a 1.8 × 10⁻³ 12 1.4 × 10⁻³ 4.3 1.4715.3 4 48** 72x 9.5 × 10⁻³ 12 7.6 × 10⁻³ 4.4 1.51 15.7 5 49** 83 2.2 ×10⁻³ 12 1.8 × 10⁻³ 4.3 1.47 15.3 4 50** 95-1 5.0 × 10⁻³ 12 4.0 × 10⁻³4.3 1.47 15.3 4 51** 109m 9.8 × 10⁻³ 12 7.8 × 10⁻³ 4.2 1.42 14.9 4 52**2b 1.8 × 10⁻³ 24 1.5 × 10⁻³ 4.2 1.42 14.9 4 53** 31a 1.9 × 10⁻³ 24 1.6 ×10⁻³ 4.6 1.59 16.5 5 54** 34a 1.6 × 10⁻³ 24 1.3 × 10⁻³ 4.5 1.54 16.1 555** 54a 2.0 × 10⁻³ 24 1.7 × 10⁻³ 4.4 1.50 15.7 5 56** 55r 6.0 × 10⁻³ 245.0 × 10⁻³ 4.6 1.59 16.5 5 57** 56a 1.8 × 10⁻³ 24 1.5 × 10⁻³ 4.3 1.4615.3 4 58** 72x 9.5 × 10⁻³ 24 8.0 × 10⁻³ 4.4 1.50 15.7 5 59** 83 2.2 ×10⁻³ 24 1.8 × 10⁻³ 4.3 1.46 15.3 4 60** 95-1 5.0 × 10⁻³ 24 4.2 × 10⁻³4.3 1.46 15.3 4 61** 109m 9.8 × 10⁻³ 24 8.2 × 10⁻³ 4.2 1.42 14.9 4 62**2b 1.8 × 10⁻³ 60 1.5 × 10⁻³ 4.2 1.43 14.9 4 63** 31a 1.9 × 10⁻³ 60 1.6 ×10⁻³ 4.7 1.59 16.6 5 64** 34a 1.6 × 10⁻³ 60 1.3 × 10⁻³ 4.5 1.55 16.2 565** 54a 2.0 × 10⁻³ 60 1.6 × 10⁻³ 4.4 1.51 15.8 5 66** 55r 6.0 × 10⁻³ 604.9 × 10⁻³ 4.7 1.59 16.6 5 67** 56a 1.8 × 10⁻³ 60 1.5 × 10⁻³ 4.3 1.4715.4 5 68** 72x 9.5 × 10⁻³ 60 7.8 × 10⁻³ 4.4 1.51 15.8 5 69** 83 2.2 ×10⁻³ 60 1.8 × 10⁻³ 4.3 1.47 15.4 5 70** 95-1 5.0 × 10⁻³ 60 4.1 × 10⁻³4.3 1.47 15.4 5 71** 109m 9.8 × 10⁻³ 60 8.0 × 10⁻³ 4.2 1.43 14.9 4 72**2b 1.8 × 10⁻³ 40 1.5 × 10⁻³ 4.2 1.43 15.0 4 73** 31a 1.9 × 10⁻³ 40 1.6 ×10⁻³ 4.7 1.60 16.7 5 74** 34a 1.6 × 10⁻³ 40 1.4 × 10⁻³ 4.6 1.56 16.3 575** 54a 2.0 × 10⁻³ 40 1.7 × 10⁻³ 4.4 1.52 15.8 5 76** 55r 6.0 × 10⁻³ 405.2 × 10⁻³ 4.7 1.60 16.7 5 77** 56a 1.8 × 10⁻³ 40 1.5 × 10⁻³ 4.3 1.4815.4 5 78** 72x 9.5 × 10⁻³ 40 8.2 × 10⁻³ 4.4 1.52 15.8 5 79** 83 2.2 ×10⁻³ 40 1.9 × 10⁻³ 4.3 1.48 15.4 5 80** 95-1 5.0 × 10⁻³ 40 4.3 × 10⁻³4.3 1.48 15.4 5 81** 109m 9.8 × 10⁻³ 40 8.4 × 10⁻³ 4.2 1.43 15.0 4 82**2b 1.8 × 10⁻³ 57 1.5 × 10⁻³ 4.2 1.42 14.9 4 83** 31a 1.9 × 10⁻³ 57 1.6 ×10⁻³ 4.6 1.59 16.6 5 84** 34a 1.6 × 10⁻³ 57 1.3 × 10⁻³ 4.5 1.55 16.2 585** 54a 2.0 × 10⁻³ 57 1.7 × 10⁻³ 4.4 1.51 15.7 5 86** 55r 6.0 × 10⁻³ 575.0 × 10⁻³ 4.6 1.59 16.6 5 87** 56a 1.8 × 10⁻³ 57 1.5 × 10⁻³ 4.3 1.4715.3 4 88** 72x 9.5 × 10⁻³ 57 8.0 × 10⁻³ 4.4 1.51 15.7 5 89** 83 2.2 ×10⁻³ 57 1.8 × 10⁻³ 4.3 1.47 15.3 4 90** 95-1 5.0 × 10⁻³ 57 4.2 × 10⁻³4.3 1.47 15.3 4 91** 109m 9.8 × 10⁻³ 57 8.2 × 10⁻³ 4.2 1.42 14.9 4*comparison **invention

It is evident from Table 31 that using hydrazine derivatives within thescope of the invention and compounds of formulae (1) to (14),thermographic recording elements satisfying all the requirements of highDmax, high contrast, and minimal black pepper are obtained.

Example 3

Samples were prepared as in Example 1 except that hydrazine derivativesand compounds of formulae (1) to (14) or comparative compounds were usedas shown in Table 32, the sensitizing dye used was a mixture of 15 mg ofSensitizing Dye D, 20 mg of Sensitizing Dye E and 18 mg of SensitizingDye F, and the support was coated with a backcoat layer having DyestuffB added so as to provide an absorbance of 0.7 at 780 nm.

The sensitizing dyes and dyestuff used in this Example are shown belowby structural formulae. They are also used in Example 4. For the sake ofconvenience, the structural formulae of compounds used in Example 4 arealso shown here.

Photographic Property Test

After the samples prepared above were exposed to xenon flash light foran emission time of 10⁻⁶ sec through an interference filter having apeak at 780 nm and a step wedge, they were processed and tested as inExample 1 except that exposure to the halogen lamp was omitted.

Black Pepper Test

The samples were rated as in Example 1.

The results are shown in Table 32.

TABLE 32 Addition Addition amount Substituted amount Hydrazine (mol/molalkene (mol/mol black compound of Ag) derivative of Ag) Dmax S γ pepper 1* — — — — 2.6 0.80 — 5  2* 10e 0.5 × 10⁻³ — — 3.5 1.20 12.5 2  3* 11g2.8 × 10⁻³ — — 3.9 1.33 13.9 3  4* 54a 1.9 × 10⁻³ — — 3.8 1.30 13.6 3 5* 56a 1.8 × 10⁻³ — — 3.7 1.27 13.2 2  6* 62g 4.5 × 10⁻³ — — 3.9 1.3313.9 3  7* 66u 9.8 × 10⁻³ — — 3.6 1.23 12.9 2  8* 95-1 6.0 × 10⁻³ — —3.7 1.27 13.2 2  9* 107a 9.5 × 10⁻³ — — 3.6 1.23 12.9 2 10* 101-5 4.8 ×10⁻³ — — 3.6 1.23 12.9 2 11* 116-12 9.6 × 10⁻³ — — 3.5 1.20 12.5 2 12*10e 0.5 × 10⁻³ VC-3 0.4 × 10⁻³ 3.7 1.26 13.2 2 13* 11g 2.8 × 10⁻³ VC-32.4 × 10⁻³ 4.1 1.40 14.7 3 14* 54a 1.9 × 10⁻³ VC-3 1.6 × 10⁻³ 4.0 1.3714.3 3 15* 56a 1.8 × 10⁻³ VC-3 1.5 × 10⁻³ 3.9 1.33 13.9 3 16* 62g 4.5 ×10⁻³ VC-3 3.8 × 10⁻³ 4.1 1.40 14.7 3 17* 66u 9.8 × 10⁻³ VC-3 8.2 × 10⁻³3.8 1.30 13.5 3 18* 95-1 6.0 × 10⁻³ VC-3 5.0 × 10⁻³ 3.9 1.33 13.9 3 19*107a 9.5 × 10⁻³ VC-3 8.0 × 10⁻³ 3.8 1.30 13.5 3 20* 101-5 4.8 × 10⁻³VC-3 4.0 × 10⁻³ 3.8 1.30 13.5 3 21* 116-12 9.6 × 10⁻³ VC-3 8.1 × 10⁻³3.7 1.26 13.2 2 22** 10e 0.5 × 10⁻³ 2 0.4 × 10⁻³ 4.1 1.41 14.8 4 23**11g 2.8 × 10⁻³ 2 2.2 × 10⁻³ 4.6 1.57 16.4 5 24** 54a 1.9 × 10⁻³ 2 1.5 ×10⁻³ 4.5 1.53 16.0 5 25** 56a 1.8 × 10⁻³ 2 1.4 × 10⁻³ 4.4 1.49 15.6 526** 62g 4.5 × 10⁻³ 2 3.5 × 10⁻³ 4.6 1.57 16.4 5 27** 66u 9.8 × 10⁻³ 27.6 × 10⁻³ 4.2 1.45 15.2 4 28** 95-1 6.0 × 10⁻³ 2 4.7 × 10⁻³ 4.4 1.4915.6 5 29** 107a 9.5 × 10⁻³ 2 7.4 × 10⁻³ 4.2 1.45 15.2 4 30** 101-5 4.8× 10⁻³ 2 3.7 × 10⁻³ 4.2 1.45 15.2 4 31** 116-12 9.6 × 10⁻³ 2 7.5 × 10⁻³4.1 1.41 14.8 4 32** 10e 0.5 × 10⁻³ 38 0.4 × 10⁻³ 4.2 1.42 14.9 4 33**11g 2.8 × 10⁻³ 38 2.2 × 10⁻³ 4.6 1.59 16.6 5 34** 54a 1.9 × 10⁻³ 38 1.5× 10⁻³ 4.5 1.55 16.2 5 35** 56a 1.8 × 10⁻³ 38 1.4 × 10⁻³ 4.4 1.51 15.7 536** 62g 4.5 × 10⁻³ 38 3.6 × 10⁻³ 4.6 1.59 16.6 5 37** 66u 9.8 × 10⁻³ 387.8 × 10⁻³ 4.3 1.47 15.3 4 38** 95-1 6.0 × 10⁻³ 38 4.8 × 10⁻³ 4.4 1.5115.7 5 39** 107a 9.5 × 10⁻³ 38 7.6 × 10⁻³ 4.3 1.47 15.3 4 40** 101-5 4.8× 10⁻³ 38 3.8 × 10⁻³ 4.3 1.47 15.3 4 41** 116-12 9.6 × 10⁻³ 38 7.7 ×10⁻³ 4.2 1.42 14.9 4 42** 10e 0.5 × 10⁻³ 12 0.4 × 10⁻³ 4.1 1.42 14.8 443** 11g 2.8 × 10⁻³ 12 2.3 × 10⁻³ 4.6 1.58 16.5 5 44** 54a 1.9 × 10⁻³ 121.6 × 10⁻³ 4.5 1.54 16.1 5 45** 56a 1.8 × 10⁻³ 12 1.5 × 10⁻³ 4.4 1.5015.6 5 46** 62g 4.5 × 10⁻³ 12 3.7 × 10⁻³ 4.6 1.58 16.5 5 47** 66u 9.8 ×10⁻³ 12 8.0 × 10⁻³ 4.3 1.46 15.2 4 48** 95-1 6.0 × 10⁻³ 12 4.9 × 10⁻³4.4 1.50 15.6 5 49** 107a 9.5 × 10⁻³ 12 7.8 × 10⁻³ 4.3 1.46 15.2 4 50**101-5 4.8 × 10⁻³ 12 3.9 × 10⁻³ 4.3 1.46 15.2 4 51** 116-12 9.6 × 10⁻³ 127.9 × 10⁻³ 4.1 1.42 14.8 4 52** 10e 0.5 × 10⁻³ 24 0.4 × 10⁻³ 4.1 1.4114.8 4 53** 11g 2.8 × 10⁻³ 24 2.3 × 10⁻³ 4.6 1.57 16.4 5 54** 54a 1.9 ×10⁻³ 24 1.6 × 10⁻³ 4.5 1.53 16.0 5 55** 56a 1.8 × 10⁻³ 24 1.5 × 10⁻³ 4.41.49 15.6 5 56** 62g 4.5 × 10⁻³ 24 3.7 × 10⁻³ 4.6 1.57 16.4 5 57** 66u9.8 × 10⁻³ 24 8.0 × 10⁻³ 4.2 1.45 15.2 4 58** 95-1 6.0 × 10⁻³ 24 4.9 ×10⁻³ 4.4 1.49 15.6 5 59** 107a 9.5 × 10⁻³ 24 7.5 × 10⁻³ 4.2 1.45 15.2 460** 101-5 4.8 × 10⁻³ 24 3.9 × 10⁻³ 4.2 1.45 15.2 4 61** 116-12 9.6 ×10⁻³ 24 7.9 × 10⁻³ 4.1 1.41 14.8 4 62** 10e 0.5 × 10⁻³ 60 0.4 × 10⁻³ 4.21.42 14.9 4 63** 11g 2.8 × 10⁻³ 60 2.2 × 10⁻³ 4.6 1.59 16.6 5 64** 54a1.9 × 10⁻³ 60 1.5 × 10⁻³ 4.5 1.55 16.2 5 65** 56a 1.8 × 10⁻³ 60 1.4 ×10⁻³ 4.4 1.51 15.7 5 66** 62g 4.5 × 10⁻³ 60 3.5 × 10⁻³ 4.6 1.59 16.6 567** 66u 9.8 × 10⁻³ 60 7.6 × 10⁻³ 4.3 1.47 15.3 4 68** 95-1 6.0 × 10⁻³60 4.7 × 10⁻³ 4.4 1.51 15.7 5 69** 107a 9.5 × 10⁻³ 60 7.4 × 10⁻³ 4.31.47 15.3 4 70** 101-5 4.8 × 10⁻³ 60 3.7 × 10⁻³ 4.3 1.47 15.3 4 71**116-12 9.6 × 10⁻³ 60 7.5 × 10⁻³ 4.2 1.42 14.9 4 72** 10e 0.5 × 10⁻³ 400.4 × 10⁻³ 4.2 1.43 14.9 4 73** 11g 2.8 × 10⁻³ 40 2.3 × 10⁻³ 4.7 1.5916.6 5 74** 54a 1.9 × 10⁻³ 40 1.6 × 10⁻³ 4.5 1.55 16.2 5 75** 56a 1.8 ×10⁻³ 40 1.5 × 10⁻³ 4.4 1.51 15.8 5 76** 62g 4.5 × 10⁻³ 40 3.7 × 10⁻³ 4.71.59 16.6 5 77** 66u 9.8 × 10⁻³ 40 8.0 × 10⁻³ 4.3 1.47 15.3 4 78** 95-16.0 × 10⁻³ 40 4.9 × 10⁻³ 4.4 1.51 15.8 5 79** 107a 9.5 × 10⁻³ 40 7.8 ×10⁻³ 4.3 1.47 15.3 4 80** 101-5 4.8 × 10⁻³ 40 3.9 × 10⁻³ 4.3 1.47 15.3 481** 116-12 9.6 × 10⁻³ 40 7.9 × 10⁻³ 4.2 1.43 14.9 4 82** 10e 0.5 × 10⁻³57 0.4 × 10⁻³ 4.1 1.42 14.8 4 83** 11g 2.8 × 10⁻³ 57 2.2 × 10⁻³ 4.6 1.5816.5 5 84** 54a 1.9 × 10⁻³ 57 1.5 × 10⁻³ 4.5 1.54 16.1 5 85** 56a 1.8 ×10⁻³ 57 1.4 × 10⁻³ 4.4 1.50 15.7 5 86** 62g 4.5 × 10⁻³ 57 3.6 × 10⁻³ 4.61.58 16.5 5 87** 66u 9.8 × 10⁻³ 57 7.8 × 10⁻³ 4.3 1.46 15.2 4 88** 95-16.0 × 10⁻³ 57 4.8 × 10⁻³ 4.4 1.50 15.7 5 89** 107a 9.5 × 10⁻³ 57 7.6 ×10⁻³ 4.3 1.46 15.2 4 90** 101-5 4.8 × 10⁻³ 57 3.8 × 10⁻³ 4.3 1.46 15.2 491** 116-12 9.6 × 10⁻³ 57 7.7 × 10⁻³ 4.1 1.42 14.8 4 *comparison**invention

It is evident from Table 32 that using hydrazine derivatives within thescope of the invention and compounds of formulae (1) to (14),thermographic recording elements satisfying all the requirements of highDmax, high contrast, and minimal black pepper are obtained.

Example 4

Samples were prepared as in Example 2 except that hydrazine derivativesand compounds of formulae (1) to (14) or comparative compounds (bothadded to the emulsion layer) were used as shown in Table 33, thesensitizing dye used was a mixture of 18 mg of Sensitizing Dye D, 15 mgof Sensitizing Dye E and 15 mg of Sensitizing Dye F, and the support wascoated with a backcoat layer having Dyestuff C added so as to provide anabsorbance of 0.7 at 780 nm.

Photographic Property Test

After the samples prepared above were exposed to xenon flash light foran emission time of 10⁻⁶ sec through an interference filter having apeak at 780 nm and a step wedge, they were processed and tested as inExample 1 except that exposure to the halogen lamp was omitted.

Black Pepper Test

The samples were rated as in Example 1.

The results are shown in Table 33.

TABLE 33 Addition Addition amount Substituted amount Hydrazine (mol/molalkene (mol/mol black compound of Ag) derivative of Ag) Dmax S γ pepper 1* — — — — 2.6 0.80 — 5  2* 1b 1.2 × 10⁻³ — — 3.4 1.16 12.1 2  3* 10a1.0 × 10⁻³ — — 3.8 1.30 13.6 3  4* 54a 2.0 × 10⁻³ — — 3.8 1.30 13.6 3 5* 56a 1.8 × 10⁻³ — — 3.6 1.23 12.9 2  6* 56r 6.3 × 10⁻³ — — 3.9 1.3313.9 3  7* 59m 7.2 × 10⁻³ — — 3.5 1.20 12.5 2  8* 95-1 6.0 × 10⁻³ — —3.7 1.27 13.2 2  9* 95-4 5.4 × 10⁻³ — — 3.5 1.20 12.5 2 10* 113-11 9.6 ×10⁻³ — — 3.6 1.23 12.9 2 11* 122 9.8 × 10⁻³ — — 3.4 1.16 12.1 2 12* 1b1.2 × 10⁻³ VC-4 1.2 × 10⁻³ 3.6 1.23 12.8 2 13* 10a 1.0 × 10⁻³ VC-4 1.0 ×10⁻³ 4.0 1.37 14.3 3 14* 54a 2.0 × 10⁻³ VC-4 2.0 × 10⁻³ 4.0 1.37 14.3 315* 56a 1.8 × 10⁻³ VC-4 1.8 × 10⁻³ 3.8 1.30 13.6 3 16* 56r 6.3 × 10⁻³VC-4 6.1 × 10⁻³ 4.1 1.41 14.7 3 17* 59m 7.2 × 10⁻³ VC-4 7.0 × 10⁻³ 3.71.26 13.2 2 18* 95-1 6.0 × 10⁻³ VC-4 5.9 × 10⁻³ 3.9 1.34 14.0 3 19* 95-45.4 × 10⁻³ VC-4 5.3 × 10⁻³ 3.7 1.26 13.2 2 20* 113-11 9.6 × 10⁻³ VC-49.4 × 10⁻³ 3.8 1.30 13.6 3 21* 122 9.8 × 10⁻³ VC-4 9.6 × 10⁻³ 3.6 1.2312.8 2 22** 1b 1.2 × 10⁻³ 1 1.0 × 10⁻³ 4.1 1.41 14.7 4 23** 10a 1.0 ×10⁻³ 1 0.8 × 10⁻³ 4.6 1.57 16.4 5 24** 54a 2.0 × 10⁻³ 1 1.6 × 10⁻³ 4.61.57 16.4 5 25** 56a 1.8 × 10⁻³ 1 1.4 × 10⁻³ 4.4 1.49 15.6 5 26** 56r6.3 × 10⁻³ 1 5.0 × 10⁻³ 4.7 1.61 16.9 5 27** 59m 7.2 × 10⁻³ 1 5.8 × 10⁻³4.2 1.45 15.1 4 28** 95-1 6.0 × 10⁻³ 1 4.8 × 10⁻³ 4.5 1.53 16.0 5 29**95-4 5.4 × 10⁻³ 1 4.3 × 10⁻³ 4.2 1.45 15.1 4 30** 113-11 9.6 × 10⁻³ 17.7 × 10⁻³ 4.4 1.49 15.6 5 31** 122 9.8 × 10⁻³ 1 7.8 × 10⁻³ 4.1 1.4114.7 4 32** 1b 1.2 × 10⁻³ 63 1.0 × 10⁻³ 4.1 1.39 14.5 4 33** 10a 1.0 ×10⁻³ 63 0.8 × 10⁻³ 4.6 1.56 16.3 5 34** 54a 2.0 × 10⁻³ 63 1.6 × 10⁻³ 4.61.56 16.3 5 35** 56a 1.8 × 10⁻³ 63 1.5 × 10⁻³ 4.3 1.48 15.4 5 36** 56r6.3 × 10⁻³ 63 5.2 × 10⁻³ 4.7 1.60 16.7 5 37** 59m 7.2 × 10⁻³ 63 5.9 ×10⁻³ 4.2 1.43 15.0 4 38** 95-1 6.0 × 10⁻³ 63 4.9 × 10⁻³ 4.4 1.52 15.8 539** 95-4 5.4 × 10⁻³ 63 4.4 × 10⁻³ 4.2 1.43 15.0 4 40** 113-11 9.6 ×10⁻³ 63 7.9 × 10⁻³ 4.3 1.48 15.4 5 41** 122 9.8 × 10⁻³ 63 8.0 × 10⁻³ 4.11.39 14.5 4 42** 1b 1.2 × 10⁻³ 7 0.9 × 10⁻³ 4.0 1.38 14.4 4 43** 10a 1.0× 10⁻³ 7 0.8 × 10⁻³ 4.5 1.55 16.1 5 44** 54a 2.0 × 10⁻³ 7 1.6 × 10⁻³ 4.51.55 16.1 5 45** 56a 1.8 × 10⁻³ 7 1.4 × 10⁻³ 4.3 1.46 15.3 4 46** 56r6.3 × 10⁻³ 7 4.9 × 10⁻³ 4.6 1.59 16.6 5 47** 59m 7.2 × 10⁻³ 7 5.6 × 10⁻³4.2 1.42 14.9 4 48** 95-1 6.0 × 10⁻³ 7 4.7 × 10⁻³ 4.4 1.51 15.7 5 49**95-4 5.4 × 10⁻³ 7 4.2 × 10⁻³ 4.2 1.42 14.9 4 50** 113-11 9.6 × 10⁻³ 77.5 × 10⁻³ 4.3 1.46 15.3 4 51** 122 9.8 × 10⁻³ 7 7.6 × 10⁻³ 4.0 1.3814.4 4 52** 1b 1.2 × 10⁻³ 14 0.9 × 10⁻³ 4.0 1.38 14.4 4 53** 10a 1.0 ×10⁻³ 14 0.8 × 10⁻³ 4.5 1.54 16.1 5 54** 54a 2.0 × 10⁻³ 14 1.5 × 10⁻³ 4.51.54 16.1 5 55** 56a 1.8 × 10⁻³ 14 1.4 × 10⁻³ 4.3 1.46 15.2 4 56** 56r6.3 × 10⁻³ 14 4.8 × 10⁻³ 4.6 1.58 16.5 5 57** 59m 7.2 × 10⁻³ 14 5.5 ×10⁻³ 4.1 1.42 14.8 4 58** 95-1 6.0 × 10⁻³ 14 4.6 × 10⁻³ 4.4 1.50 15.7 559** 95-4 5.4 × 10⁻³ 14 4.1 × 10⁻³ 4.1 1.42 14.8 4 60** 113-11 9.6 ×10⁻³ 14 7.3 × 10⁻³ 4.3 1.46 15.2 4 61** 122 9.8 × 10⁻³ 14 7.4 × 10⁻³ 4.01.38 14.4 4 62** 1b 1.2 × 10⁻³ 37 1.0 × 10⁻³ 4.1 1.39 14.5 4 63** 10a1.0 × 10⁻³ 37 0.8 × 10⁻³ 4.5 1.55 16.2 5 64** 54a 2.0 × 10⁻³ 37 1.6 ×10⁻³ 4.5 1.55 16.2 5 65** 56a 1.8 × 10⁻³ 37 1.4 × 10⁻³ 4.3 1.47 15.3 466** 56r 6.3 × 10⁻³ 37 5.0 × 10⁻³ 4.7 1.59 16.6 5 67** 59m 7.2 × 10⁻³ 375.8 × 10⁻³ 4.2 1.43 14.9 4 68** 95-1 6.0 × 10⁻³ 37 4.8 × 10⁻³ 4.4 1.5115.8 5 69** 95-4 5.4 × 10⁻³ 37 4.3 × 10⁻³ 4.2 1.43 14.9 4 70** 113-119.6 × 10⁻³ 37 7.7 × 10⁻³ 4.3 1.47 15.3 4 71** 122 9.8 × 10⁻³ 37 7.8 ×10⁻³ 4.1 1.39 14.5 4 72** 1b 1.2 × 10⁻³ 39 1.0 × 10⁻³ 4.1 1.39 14.5 473** 10a 1.0 × 10⁻³ 39 0.8 × 10⁻³ 4.5 1.56 16.2 5 74** 54a 2.0 × 10⁻³ 391.7 × 10⁻³ 4.5 1.56 16.2 5 75** 56a 1.8 × 10⁻³ 39 1.5 × 10⁻³ 4.3 1.4715.4 5 76** 56r 6.3 × 10⁻³ 39 5.3 × 10⁻³ 4.7 1.60 16.7 5 77** 59m 7.2 ×10⁻³ 39 6.0 × 10⁻³ 4.2 1.43 15.0 4 78** 95-1 6.0 × 10⁻³ 39 5.0 × 10⁻³4.4 1.52 15.8 5 79** 95-4 5.4 × 10⁻³ 39 4.5 × 10⁻³ 4.2 1.43 15.0 4 80**113-11 9.6 × 10⁻³ 39 8.1 × 10⁻³ 4.3 1.47 15.4 5 81** 122 9.8 × 10⁻³ 398.2 × 10⁻³ 4.1 1.39 14.5 4 82** 1b 1.2 × 10⁻³ 41 1.0 × 10⁻³ 4.0 1.3814.5 4 83** 10a 1.0 × 10⁻³ 41 0.8 × 10⁻³ 4.5 1.55 16.2 5 84** 54a 2.0 ×10⁻³ 41 1.6 × 10⁻³ 4.5 1.55 16.2 5 85** 56a 1.8 × 10⁻³ 41 1.5 × 10⁻³ 4.31.47 15.3 4 86** 56r 6.3 × 10⁻³ 41 5.2 × 10⁻³ 4.6 1.59 16.6 5 87** 59m7.2 × 10⁻³ 41 5.9 × 10⁻³ 4.2 1.42 14.9 4 88** 95-1 6.0 × 10⁻³ 41 4.9 ×10⁻³ 4.4 1.51 15.7 5 89** 95-4 5.4 × 10⁻³ 41 4.4 × 10⁻³ 4.2 1.42 14.9 490** 113-11 9.6 × 10⁻³ 41 7.9 × 10⁻³ 4.3 1.47 15.3 4 91** 122 9.8 × 10⁻³41 8.0 × 10⁻³ 4.0 1.38 14.5 4 *comparison **invention

It is evident from Table 33 that using hydrazine derivatives within thescope of the invention and compounds of formulae (1) to (14),thermographic recording elements satisfying all the requirements of highDmax, high contrast, and minimal black pepper are obtained.

Example 5

Samples were prepared as in Example 3 except that hydrazine derivativesand compounds of formulae (1) to (14) or comparative compounds were usedas shown in Table 34.

Photographic Property Test

The samples were examined as in Example 3.

Black Pepper Test

The samples were rated as in Example 1.

The results are shown in Table 34.

TABLE 34 Addition Addition amount Substituted amount Hydrazine (mol/molalkene (mol/mol black compound of Ag) derivative of Ag) Dmax S γ pepper 1* — — — — 2.6 0.80 — 5  2* 11g 1.5 × 10⁻⁵ — — 3.6 1.13 12.7 2  3* 72y7.5 × 10⁻⁵ — — 3.4 1.06 12.0 3  4* 85 1.5 × 10⁻⁵ — — 3.7 1.16 13.1 3  5*106-10 7.5 × 10⁻⁵ — — 3.5 1.09 12.4 2  6* 122 7.5 × 10⁻⁵ — — 3.4 1.0612.0 3  7* 125a 1.5 × 10⁻⁵ — — 3.6 1.13 12.7 2  8* 130c 1.5 × 10⁻⁵ — —3.7 1.16 13.1 2  9* — — VC-2 2.5 × 10⁻³ 3.3 1.03 11.7 3 10** — — 1 2.5 ×10⁻³ 3.7 1.19 14.8 4 11** — — 60 2.5 × 10⁻³ 4.2 1.40 16.0 5 12** — — 122.5 × 10⁻³ 3.9 1.20 15.2 5 13** — — 45 2.5 × 10⁻³ 4.0 1.39 15.0 4 14** —— 50 2.5 × 10⁻³ 4.2 1.40 16.5 5 15** — — 52 2.5 × 10⁻³ 3.8 1.31 15.5 416** — — 58 2.5 × 10⁻³ 3.9 1.30 15.7 4 17** — — 59 2.5 × 10⁻³ 3.7 1.2915.5 4 18* 11g 1.5 × 10⁻⁵ VC-2 1.8 × 10⁻⁴ 3.7 1.16 13.1 3 19* 71y 7.5 ×10⁻⁵ VC-2 1.8 × 10⁻⁴ 3.5 1.09 12.4 3 20* 85 1.5 × 10⁻⁵ VC-2 1.8 × 10⁻⁴3.8 1.19 13.4 3 21* 106-10 7.5 × 10⁻⁵ VC-2 1.8 × 10⁻⁴ 3.6 1.13 12.7 322* 122 7.5 × 10⁻⁵ VC-2 1.8 × 10⁻⁴ 3.5 1.09 12.4 3 23* 125a 1.5 × 10⁻⁵VC-2 1.8 × 10⁻⁴ 3.7 1.16 13.1 3 24* 130c 1.5 × 10⁻⁵ VC-2 1.8 × 10⁻⁴ 3.81.19 13.4 3 25** 11g 1.5 × 10⁻⁵ 1 1.8 × 10⁻⁴ 4.1 1.36 15.4 4 26** 72y7.5 × 10⁻⁵ 1 1.8 × 10⁻⁴ 3.8 1.29 14.6 5 27** 85 1.5 × 10⁻⁵ 1 1.8 × 10⁻⁴4.2 1.40 15.8 5 28** 106-10 7.5 × 10⁻⁵ 1 1.8 × 10⁻⁴ 3.9 1.33 15.0 4 29**122 7.5 × 10⁻⁵ 1 1.8 × 10⁻⁴ 3.8 1.29 14.6 5 30** 125a 1.5 × 10⁻⁵ 1 1.8 ×10⁻⁴ 4.1 1.36 15.4 5 31** 130c 1.5 × 10⁻⁵ 1 1.8 × 10⁻⁴ 4.2 1.40 15.8 532** 11g 1.5 × 10⁻⁵ 60 1.8 × 10⁻⁴ 4.1 1.39 15.7 4 33** 72y 7.5 × 10⁻⁵ 601.8 × 10⁻⁴ 3.9 1.31 14.8 5 34** 85 1.5 × 10⁻⁵ 60 1.8 × 10⁻⁴ 4.3 1.4316.1 5 35** 106-10 7.5 × 10⁻⁵ 60 1.8 × 10⁻⁴ 4.0 1.35 15.3 4 36** 122 7.5× 10⁻⁵ 60 1.8 × 10⁻⁴ 3.9 1.31 14.8 5 37** 125a 1.5 × 10⁻⁵ 60 1.8 × 10⁻⁴4.1 1.39 15.7 5 38** 130c 1.5 × 10⁻⁵ 60 1.8 × 10⁻⁴ 4.3 1.43 16.1 5 39**11g 1.5 × 10⁻⁵ 12 1.8 × 10⁻⁴ 4.0 1.34 15.2 4 40** 72y 7.5 × 10⁻⁵ 12 1.8× 10⁻⁴ 3.8 1.27 14.3 5 41** 85 1.5 × 10⁻⁵ 12 1.8 × 10⁻⁴ 4.1 1.38 15.6 542** 106-10 7.5 × 10⁻⁵ 12 1.8 × 10⁻⁴ 3.9 1.31 14.7 4 43** 122 7.5 × 10⁻⁵12 1.8 × 10⁻⁴ 3.8 1.27 14.3 5 44** 125a 1.5 × 10⁻⁵ 12 1.8 × 10⁻⁴ 4.01.34 15.2 5 45** 130c 1.5 × 10⁻⁵ 12 1.8 × 10⁻⁴ 4.1 1.38 15.6 5 46** 11g1.5 × 10⁻⁵ 45 1.8 × 10⁻⁴ 4.2 1.42 16.0 4 47** 72y 7.5 × 10⁻⁵ 45 1.8 ×10⁻⁴ 4.0 1.34 15.1 5 48** 85 1.5 × 10⁻⁵ 45 1.8 × 10⁻⁴ 4.3 1.45 16.4 549** 106-10 7.5 × 10⁻⁵ 45 1.8 × 10⁻⁴ 4.1 1.38 15.6 4 50** 122 7.5 × 10⁻⁵45 1.8 × 10⁻⁴ 4.0 1.34 15.1 5 51** 125a 1.5 × 10⁻⁵ 45 1.8 × 10⁻⁴ 4.21.42 16.0 5 52** 130c 1.5 × 10⁻⁵ 45 1.8 × 10⁻⁴ 4.3 1.45 16.4 5 53** 11g1.5 × 10⁻⁵ 50 1.8 × 10⁻⁴ 4.4 1.47 16.5 5 54** 72y 7.5 × 10⁻⁵ 50 1.8 ×10⁻⁴ 4.1 1.38 15.6 5 55** 85 1.5 × 10⁻⁵ 50 1.8 × 10⁻⁴ 4.5 1.51 17.0 556** 106-10 7.5 × 10⁻⁵ 50 1.8 × 10⁻⁴ 4.2 1.42 16.1 4 57** 122 7.5 × 10⁻⁵50 1.8 × 10⁻⁴ 4.1 1.38 15.6 5 58** 125a 1.5 × 10⁻⁵ 50 1.8 × 10⁻⁴ 4.41.47 16.5 5 59** 130c 1.5 × 10⁻⁵ 50 1.8 × 10⁻⁴ 4.5 1.51 17.0 5 60** 11g1.5 × 10⁻⁵ 52 1.8 × 10⁻⁴ 4.2 1.42 16.1 4 61** 72y 7.5 × 10⁻⁵ 52 1.8 ×10⁻⁴ 4.0 1.35 15.2 5 62** 85 1.5 × 10⁻⁵ 52 1.8 × 10⁻⁴ 4.4 1.46 16.5 563** 106-10 7.5 × 10⁻⁵ 52 1.8 × 10⁻⁴ 4.1 1.39 15.6 4 64** 122 7.5 × 10⁻⁵52 1.8 × 10⁻⁴ 4.0 1.35 15.2 5 65** 125a 1.5 × 10⁻⁵ 52 1.8 × 10⁻⁴ 4.21.42 16.1 5 66** 130c 1.5 × 10⁻⁵ 52 1.8 × 10⁻⁴ 4.4 1.46 16.5 5 67** 11g1.5 × 10⁻⁵ 58 1.8 × 10⁻⁴ 4.3 1.44 16.2 5 68** 72y 7.5 × 10⁻⁵ 58 1.8 ×10⁻⁴ 4.0 1.36 15.3 5 69** 85 1.5 × 10⁻⁵ 58 1.8 × 10⁻⁴ 4.4 1.47 16.7 570** 106-10 7.5 × 10⁻⁵ 58 1.8 × 10⁻⁴ 4.2 1.40 15.8 4 71** 122 7.5 × 10⁻⁵58 1.8 × 10⁻⁴ 4.0 1.36 15.3 5 72** 125a 1.5 × 10⁻⁵ 58 1.8 × 10⁻⁴ 4.31.44 16.2 5 73** 130c 1.5 × 10⁻⁵ 58 1.8 × 10⁻³ 4.4 1.47 16.7 5 74** 11g1.5 × 10⁻⁵ 59 1.8 × 10⁻⁴ 4.1 1.39 15.7 4 75** 72y 7.5 × 10⁻⁵ 59 1.8 ×10⁻⁴ 3.9 1.31 14.8 5 76** 85 1.5 × 10⁻⁵ 59 1.8 × 10⁻⁴ 4.2 1.43 16.1 577** 106-10 7.5 × 10⁻⁵ 59 1.8 × 10⁻⁴ 4.0 1.35 15.3 4 78** 122 7.5 × 10⁻⁵59 1.8 × 10⁻⁴ 3.9 1.31 14.8 5 79** 125a 1.5 × 10⁻⁵ 59 1.8 × 10⁻⁴ 4.11.39 15.7 5 80** 130c 1.5 × 10⁻⁵ 59 1.8 × 10⁻⁴ 4.2 1.43 16.1 5*comparison **invention

It is evident from Table 34 that using compounds of formulae (1) to (14)according to the invention, thermographic recording elements satisfyingall the requirements of high Dmax, high contrast, and minimal blackpepper are obtained.

Example 6

Samples were prepared as in Example 4 except that hydrazine derivativesand compounds of formulae (1) to (14) or comparative compounds were usedas shown in Table 35.

Photographic Property Test

The samples were examined as in Example 3.

Black Pepper Test

The samples were rated as in Example 1.

The results are shown in Table 35.

TABLE 35 Addition Addition amount Substituted amount Hydrazine (mol/molalkene (mol/mol black compound of Ag) derivative of Ag) Dmax S γ pepper 1* — — — — 2.6 0.80 — 5  2* 11g 1.5 × 10⁻⁵ — — 3.6 1.14 12.8 2  3* 72y7.5 × 10⁻⁵ — — 3.4 1.07 12.1 3  4* 85 1.5 × 10⁻⁵ — — 3.7 1.17 13.2 3  5*106-10 7.5 × 10⁻⁵ — — 3.5 1.11 12.5 2  6* 122 7.5 × 10⁻⁵ — — 3.4 1.0712.1 3  7* 125a 1.5 × 10⁻⁵ — — 3.6 1.14 12.8 2  8* 130c 1.5 × 10⁻⁵ — —3.7 1.17 13.2 2  9* — — VC-6 2.5 × 10⁻³ 3.3 1.04 11.8 3 10** — — 2 2.5 ×10⁻³ 4.0 1.35 14.9 4 11** — — 38 2.5 × 10⁻³ 4.0 1.36 15.0 4 12** — — 572.5 × 10⁻³ 4.0 1.33 15.5 5 13** — — 46 2.5 × 10⁻³ 3.9 1.35 15.3 4 14** —— 47 2.5 × 10⁻³ 4.1 1.40 15.5 5 15** — — 51 2.5 × 10⁻³ 4.3 1.48 16.6 516** — — 55 2.5 × 10⁻³ 4.0 1.39 15.7 5 17** — — 64 2.5 × 10⁻³ 4.1 1.3915.8 4 18* 11g 1.5 × 10⁻⁵ VC-6 1.8 × 10⁻⁴ 3.7 1.17 13.2 3 19* 72y 7.5 ×10⁻⁵ VC-6 1.8 × 10⁻⁴ 3.5 1.10 12.5 3 20* 85 1.5 × 10⁻⁵ VC-6 1.8 × 10⁻⁴3.9 1.20 13.6 3 21* 106-10 7.5 × 10⁻⁵ VC-6 1.8 × 10⁻⁴ 3.6 1.14 12.8 322* 122 7.5 × 10⁻⁵ VC-6 1.8 × 10⁻⁴ 3.5 1.10 12.5 3 23* 125a 1.5 × 10⁻⁵VC-6 1.8 × 10⁻⁴ 3.7 1.17 13.2 3 24* 130c 1.5 × 10⁻⁵ VC-6 1.8 × 10⁻⁴ 3.91.20 13.6 3 25** 11g 1.5 × 10⁻⁵ 2 1.8 × 10⁻⁴ 4.1 1.38 15.5 4 26** 72y7.5 × 10⁻⁵ 2 1.8 × 10⁻⁴ 3.9 1.30 14.7 5 27** 85 1.5 × 10⁻⁵ 2 1.8 × 10⁻⁴4.2 1.41 16.0 5 28** 106-10 7.5 × 10⁻⁵ 2 1.8 × 10⁻⁴ 4.0 1.34 15.1 4 29**122 7.5 × 10⁻⁵ 2 1.8 × 10⁻⁴ 3.9 1.30 14.7 5 30** 125a 1.5 × 10⁻⁵ 2 1.8 ×10⁻⁴ 4.1 1.38 15.5 5 31** 130c 1.5 × 10⁻⁵ 2 1.8 × 10⁻⁴ 4.2 1.41 16.0 532** 11g 1.5 × 10⁻⁵ 38 1.8 × 10⁻⁴ 4.2 1.40 15.9 4 33** 72y 7.5 × 10⁻⁵ 381.8 × 10⁻⁴ 4.0 1.33 15.0 5 34** 85 1.5 × 10⁻⁵ 38 1.8 × 10⁻⁴ 4.3 1.4416.3 5 35** 106-10 7.5 × 10⁻⁵ 38 1.8 × 10⁻⁴ 4.1 1.37 15.4 4 36** 122 7.5× 10⁻⁵ 38 1.8 × 10⁻⁴ 4.0 1.33 15.0 5 37** 125a 1.5 × 10⁻⁵ 38 1.8 × 10⁻⁴4.2 1.40 15.9 5 38** 130c 1.5 × 10⁻⁵ 38 1.8 × 10⁻⁴ 4.3 1.44 16.3 5 39**11g 1.5 × 10⁻⁵ 57 1.8 × 10⁻⁴ 4.0 1.35 15.3 4 40** 72y 7.5 × 10⁻⁵ 57 1.8× 10⁻⁴ 3.8 1.28 14.5 5 41** 85 1.5 × 10⁻⁵ 57 1.8 × 10⁻⁴ 4.1 1.39 15.7 542** 106-10 7.5 × 10⁻⁵ 57 1.8 × 10⁻⁴ 3.9 1.32 14.9 4 43** 122 7.5 × 10⁻⁵57 1.8 × 10⁻⁴ 3.8 1.28 14.5 5 44** 125a 1.5 × 10⁻⁵ 57 1.8 × 10⁻⁴ 4.01.35 15.3 5 45** 130c 1.5 × 10⁻⁵ 57 1.8 × 10⁻⁴ 4.1 1.39 15.7 5 46** 11g1.5 × 10⁻⁵ 46 1.8 × 10⁻⁴ 4.3 1.43 16.1 4 47** 72y 7.5 × 10⁻⁵ 46 1.8 ×10⁻⁴ 4.0 1.35 15.3 5 48** 85 1.5 × 10⁻⁵ 46 1.8 × 10⁻⁴ 4.4 1.47 16.6 549** 106-10 7.5 × 10⁻⁵ 46 1.8 × 10⁻⁴ 4.1 1.39 15.7 4 50** 122 7.5 × 10⁻⁵46 1.8 × 10⁻⁴ 4.0 1.35 15.3 5 51** 125a 1.5 × 10⁻⁵ 46 1.8 × 10⁻⁴ 4.31.43 16.1 5 52** 130c 1.5 × 10⁻⁵ 46 1.8 × 10⁻⁴ 4.4 1.47 16.6 5 53** 11g1.5 × 10⁻⁵ 47 1.8 × 10⁻⁴ 4.4 1.48 16.7 5 54** 72y 7.5 × 10⁻⁵ 47 1.8 ×10⁻⁴ 4.2 1.40 15.8 5 55** 85 1.5 × 10⁻⁵ 47 1.8 × 10⁻⁴ 4.5 1.52 17.2 556** 106-10 7.5 × 10⁻⁵ 47 1.8 × 10⁻⁴ 4.3 1.44 16.2 4 57** 122 7.5 × 10⁻⁵47 1.8 × 10⁻⁴ 4.2 1.40 15.8 5 58** 125a 1.5 × 10⁻⁵ 47 1.8 × 10⁻⁴ 4.41.48 16.7 5 59** 130c 1.5 × 10⁻⁵ 47 1.8 × 10⁻⁴ 4.5 1.52 17.2 5 60** 11g1.5 × 10⁻⁵ 51 1.8 × 10⁻⁴ 4.3 1.44 16.2 4 61** 72y 7.5 × 10⁻⁵ 51 1.8 ×10⁻⁴ 4.0 1.36 15.4 5 62** 85 1.5 × 10⁻⁵ 51 1.8 × 10⁻⁴ 4.4 1.48 16.7 563** 106-10 7.5 × 10⁻⁵ 51 1.8 × 10⁻⁴ 4.2 1.40 15.8 4 64** 122 7.5 × 10⁻⁵51 1.8 × 10⁻⁴ 4.0 1.36 15.4 5 65** 125a 1.5 × 10⁻⁵ 51 1.8 × 10⁻⁴ 4.31.44 16.2 5 66** 130c 1.5 × 10⁻⁵ 51 1.8 × 10⁻⁴ 4.4 1.48 16.7 5 67** 11g1.5 × 10⁻⁵ 55 1.8 × 10⁻⁴ 4.3 1.45 16.4 5 68** 72y 7.5 × 10⁻⁵ 55 1.8 ×10⁻⁴ 4.1 1.37 15.5 5 69** 85 1.5 × 10⁻⁵ 55 1.8 × 10⁻⁴ 4.4 1.49 16.8 570** 106-10 7.5 × 10⁻⁵ 55 1.8 × 10⁻⁴ 4.2 1.41 15.9 4 71** 122 7.5 × 10⁻⁵55 1.8 × 10⁻⁴ 4.1 1.37 15.5 5 72** 125a 1.5 × 10⁻⁵ 55 1.8 × 10⁻⁴ 4.31.45 16.4 5 73** 130c 1.5 × 10⁻⁵ 55 1.8 × 10⁻⁴ 4.4 1.49 16.8 5 74** 11g1.5 × 10⁻⁵ 64 1.8 × 10⁻⁴ 4.2 1.40 15.9 4 75** 72y 7.5 × 10⁻⁵ 64 1.8 ×10⁻⁴ 4.0 1.33 15.0 5 76** 85 1.5 × 10⁻⁵ 64 1.8 × 10⁻⁴ 4.3 1.44 16.3 577** 106-10 7.5 × 10⁻⁵ 64 1.8 × 10⁻⁴ 4.1 1.37 15.4 4 78** 122 7.5 × 10⁻⁵64 1.8 × 10⁻⁴ 4.0 1.33 15.0 5 79** 125a 1.5 × 10⁻⁵ 64 1.8 × 10⁻⁴ 4.21.40 15.9 5 80** 130c 1.5 × 10⁻⁵ 64 1.8 × 10⁻⁴ 4.3 1.44 16.3 5*comparison **invention

It is evident from Table 35 that using compounds of formulae (1) to (14)according to the invention, thermographic recording elements satisfyingall the requirements of high Dmax, high contrast, and minimal blackpepper are obtained.

Example 7 Silver Halide Emulsion C

In 700 ml of water were dissolved 22 grams of phthalated gelatin and 30mg of potassium bromide. The solution was adjusted to pH 5.0 at atemperature of 40° C. To the solution, 159 ml of an aqueous solutioncontaining 18.6 grams of silver nitrate and an aqueous solutioncontaining potassium bromide were added over 10 minutes by thecontrolled double jet method while maintaining the solution at pAg 7.7.Then, an aqueous solution containing 8×10⁻⁶ mol/liter of K₃[IrCl₆] and 1mol/liter of potassium bromide was added over 30 minutes by thecontrolled double jet method while maintaining the solution at pAg 7.7.The emulsion was adjusted to pH 5.9 and pAg 8.0. There were obtainedcubic grains having a mean grain size of 0.07 μm, a coefficient ofvariation of the projected area diameter of 8%, and a (100) faceproportion of 86%.

The thus obtained silver halide grains C were heated at 60° C., to which8.5×10⁻⁵ mol of sodium thiosulfate, 1.1×10⁻⁵ mol of2,3,4,5,6-pentafluorophenyldiphenylsulfin selenide, 2×10⁻⁶ mol ofTellurium Compound 1, 3.3×10⁻⁶ mol of chloroauric acid, and 2.3×10⁻⁴ molof thiocyanic acid were added per mol of silver. The emulsion wasripened for 120 minutes and then quenched to 50° C. With stirring,8×10⁻⁴ mol of Sensitizing Dye G was added, and 3.5×10⁻² mol of potassiumiodide was added to the emulsion, which was stirred for 30 minutes andthen quenched to 30° C., completing the preparation of a silver halideemulsion C.

Organic Acid Silver Microcrystalline Dispersion

A mixture of 40 grams of behenic acid, 7.3 grams of stearic acid, and500 ml of distilled water was stirred at 90° C. for 15 minutes. Withvigorous stirring, 187 ml of 1N NaOH aqueous solution was added over 15minutes, 61 ml of 1N nitric acid was added, and the solution was cooledto 50° C. Then, 124 ml of an aqueous solution of 1N silver nitrate wasadded and stirring was continued for 30 minutes. Thereafter, the solidswere separated by suction filtration and washed with water until thewater filtrate reached a conductivity of 30 μS/cm. The thus obtainedsolids were handled as a wet cake without drying. To 34.8 grams as drysolids of the wet cake were added 12 grams of polyvinyl alcohol and 150ml of water. They were thoroughly mixed to form a slurry. A vessel wascharged with the slurry together with 840 grams of zirconia beads havinga mean diameter of 0.5 mm. A dispersing machine (¼G Sand Grinder Mill byImex K.K.) was operated for 5 hours for dispersion, completing thepreparation of a microcrystalline dispersion of organic acid silvergrains having a volume weighed mean grain diameter of 1.5 μm as measuredby Master Sizer X (Malvern Instruments Ltd.).

Solid Particle Dispersions of Chemical Addenda

Solid particle dispersions of tetrachlorophthalic acid (C-7),4-methylphthalic acid (C-8),1,1-bis(2-hydroxy-3,5-dimethylphenyl)-3,5,5-trimethylhexane (C-5),phthalazine (C-6), and tribromomethylsulfonylbenzene (C-14) wereprepared.

To tetrachlorophthalic acid were added 0.81 gram of hydroxypropylcellulose and 94.2 ml of water. They were thoroughly agitated to form aslurry, which was allowed to stand for 10 hours. A vessel was chargedwith the slurry together with 100 ml of zirconia beads having a meandiameter of 0.5 mm. A dispersing machine as above was operated for 5hours for dispersion, obtaining a solid particle dispersion oftetrachlorophthalic acid in which particles with a diameter of up to 1.0μm accounted for 70% by weight. Solid particle dispersions of theremaining chemical addenda were similarly prepared by properly changingthe amount of dispersant and the dispersion time to achieve a desiredmean particle size.

Emulsion Layer Coating Solution

An emulsion layer coating solution was prepared by adding the followingcompositions to the organic acid silver microparticulate dispersionprepared above.

Organic acid silver particle dispersion 1 mol Silver halide emulsion C0.05 mol Binder: LACSTAR 3307B SBR latex 430 g Addenda for development:5 g Tetrachlorophthalic acid 1,1-bis(2-hydroxy-3,5-dimethylphenyl)- 98 g3,5,5-trimethylhexane Phthalazine 9.2 g Tribromomethylphenylsulfone 12 g4-methylphthalic acid 7 g

Hydrazine derivative (see Table 36)

Inventive compound (see Table 36)

Comparative compound (see Table 36)

Note that the type and amount of hydrazine derivative, inventivecompound and comparative compound added are shown in Table 36, theamount being expressed by mol per mol of silver.

Emulsion Surface Protective Layer Coating Solution

An emulsion surface protective layer coating solution was prepared byadding 0.26 gram of Surfactant A, 0.09 gram of Surfactant B, 0.9 gram ofsilica microparticulates having a mean particle size of 2.5 μm, 0.3 gramof 1,2-bis(vinylsulfonylacetamide)ethane and 64 grams of water to 10grams of inert gelatin.

Coated Sample

A back layer coating solution was prepared by adding 6 grams ofpolyvinyl butyral Denka Butyral #4000-2, 0.2 gram of spherical silicaSildex H121 (mean size 12 μm), 0.2 gram of spherical silica Sildex H51(mean size 5 μm), and 0.1 gram of Megafax F-176P to 64 grams of2-propanol and mixing them into a solution. Further, a mixed solution of420 mg of Dyestuff B in 10 grams of methanol and 20 grams of acetone anda solution of 0.8 gram of 3-isocyanatomethyl-3,5,5-trimethylhexylisocyanate in 6 grams of ethyl acetate were added to the solution.

A polyethylene terephthalate film having a moisture-proof undercoat ofvinylidene chloride on either surface was coated on one surface with theback surface coating solution so as to give an optical density of 0.7 at780 nm.

On the thus prepared support, the emulsion layer coating solution wascoated so as to give a coverage of 1.6 g/m² of silver, and the emulsionlayer protective layer coating solution was then coated on the emulsionlayer so as to give a gelatin coverage of 1.8 g/m², obtaining a coatedsample.

Photographic Property Test

The samples were examined as in Example 1.

Black Pepper Test

The samples were rated as in Example 1.

The results are shown in Table 36.

TABLE 36 Addition Addition amount Substituted amount Hydrazine (mol/molalkene (mol/mol black compound of Ag) derivative of Ag) Dmax S γ pepper 1* — — — — 2.6 0.80 — 5  2* 11g 2.5 × 10⁻⁴ — — 3.7 1.15 10.7 2  3* 72y5.0 × 10⁻⁴ — — 3.5 1.09 10.1 3  4* 85 2.5 × 10⁻⁴ — — 3.8 1.18 11.0 3  5*106-10 5.0 × 10⁻⁴ — — 3.6 1.12 10.4 2  6* 122 5.0 × 10⁻⁴ — — 3.5 1.0910.1 3  7* 125a 2.5 × 10⁻⁴ — — 3.7 1.15 10.7 2  8* 130c 2.5 × 10⁻⁴ — —3.8 1.18 11.0 2  9* — — VC-5 7.5 × 10⁻³ 3.4 1.05 9.8 3 10** — — 2 7.5 ×10⁻³ 4.0 1.33 12.9 4 11** — — 38 7.5 × 10⁻³ 4.1 1.38 13.0 4 12** — — 577.5 × 10⁻³ 4.1 1.32 12.5 5 13** — — 46 7.5 × 10⁻³ 4.2 1.40 13.0 4 14** —— 47 7.5 × 10⁻³ 4.5 1.41 13.8 5 15** — — 51 7.5 × 10⁻³ 4.5 1.48 13.9 516** — — 55 7.5 × 10⁻³ 4.3 1.39 12.4 4 17** — — 64 7.5 × 10⁻³ 4.0 1.3713.0 4 18* 11g 2.5 × 10⁻⁴ VC-5 3.6 × 10⁻⁴ 3.8 1.18 11.0 3 19* 72y 5.0 ×10⁻⁴ VC-5 3.6 × 10⁻⁴ 3.6 1.12 10.4 3 20* 85 2.5 × 10⁻⁴ VC-5 3.6 × 10⁻⁴3.9 1.21 11.3 3 21* 106-10 5.0 × 10⁻⁴ VC-5 3.6 × 10⁻⁴ 3.7 1.15 10.7 322* 122 5.0 × 10⁻⁴ VC-5 3.6 × 10⁻⁴ 3.6 1.12 10.4 3 23* 125a 2.5 × 10⁻⁴VC-5 3.6 × 10⁻⁴ 3.8 1.18 11.0 3 24* 130c 2.5 × 10⁻⁴ VC-5 3.6 × 10⁻⁴ 3.91.21 11.3 3 25** 11g 2.5 × 10⁻⁴ 2 3.6 × 10⁻⁴ 4.2 1.39 12.9 4 26** 72y5.0 × 10⁻⁴ 2 3.6 × 10⁻⁴ 3.9 1.32 12.2 5 27** 85 2.5 × 10⁻⁴ 2 3.6 × 10⁻⁴4.3 1.43 13.3 5 28** 106-10 5.0 × 10⁻⁴ 2 3.6 × 10⁻⁴ 4.0 1.35 12.6 4 29**122 5.0 × 10⁻⁴ 2 3.6 × 10⁻⁴ 3.9 1.32 12.2 5 30** 125a 2.5 × 10⁻⁴ 2 3.6 ×10⁻⁴ 4.2 1.39 12.9 5 31** 130c 2.5 × 10⁻⁴ 2 3.6 × 10⁻⁴ 4.3 1.43 13.3 532** 11g 2.5 × 10⁻⁴ 38 3.6 × 10⁻⁴ 4.2 1.42 13.2 4 33** 72y 5.0 × 10⁻⁴ 383.6 × 10⁻⁴ 4.0 1.34 12.5 5 34** 85 2.5 × 10⁻⁴ 38 3.6 × 10⁻⁴ 4.4 1.4613.6 5 35** 106-10 5.0 × 10⁻⁴ 38 3.6 × 10⁻⁴ 4.1 1.38 12.8 4 36** 122 5.0× 10⁻⁴ 38 3.6 × 10⁻⁴ 4.0 1.34 12.5 5 37** 125a 2.5 × 10⁻⁴ 38 3.6 × 10⁻⁴4.2 1.42 13.2 5 38** 130c 2.5 × 10⁻⁴ 38 3.6 × 10⁻⁴ 4.4 1.46 13.6 5 39**11g 2.5 × 10⁻⁴ 57 3.6 × 10⁻⁴ 4.1 1.37 12.7 4 40** 72y 5.0 × 10⁻⁴ 57 3.6× 10⁻⁴ 3.9 1.29 12.0 5 41** 85 2.5 × 10⁻⁴ 57 3.6 × 10⁻⁴ 4.2 1.41 13.1 542** 106-10 5.0 × 10⁻⁴ 57 3.6 × 10⁻⁴ 4.0 1.33 12.4 4 43** 122 5.0 × 10⁻⁴57 3.6 × 10⁻⁴ 3.9 1.29 12.0 5 44** 125a 2.5 × 10⁻⁴ 57 3.6 × 10⁻⁴ 4.11.37 12.7 5 45** 130c 2.5 × 10⁻⁴ 57 3.6 × 10⁻⁴ 4.2 1.41 13.1 5 46** 11g2.5 × 10⁻⁴ 46 3.6 × 10⁻⁴ 4.3 1.45 13.4 4 47** 72y 5.0 × 10⁻⁴ 46 3.6 ×10⁻⁴ 4.1 1.37 12.7 5 48** 85 2.5 × 10⁻⁴ 46 3.6 × 10⁻⁴ 4.4 1.48 13.8 549** 106-10 5.0 × 10⁻⁴ 46 3.6 × 10⁻⁴ 4.2 1.41 13.1 4 50** 122 5.0 × 10⁻⁴46 3.6 × 10⁻⁴ 4.1 1.37 12.7 5 51** 125a 2.5 × 10⁻⁴ 46 3.6 × 10⁻⁴ 4.31.45 13.4 5 52** 130c 2.5 × 10⁻⁴ 46 3.6 × 10⁻⁴ 4.4 1.48 13.8 5 53** 11g2.5 × 10⁻⁴ 47 3.6 × 10⁻⁴ 4.5 1.50 13.9 5 54** 72y 5.0 × 10⁻⁴ 47 3.6 ×10⁻⁴ 4.2 1.41 13.1 5 55** 85 2.5 × 10⁻⁴ 47 3.6 × 10⁻⁴ 4.6 1.54 14.3 556** 106-10 5.0 × 10⁻⁴ 47 3.6 × 10⁻⁴ 4.4 1.45 13.5 4 57** 122 5.0 × 10⁻⁴47 3.6 × 10⁻⁴ 4.2 1.41 13.1 5 58** 125a 2.5 × 10⁻⁴ 47 3.6 × 10⁻⁴ 4.51.50 13.9 5 59** 130c 2.5 × 10⁻⁴ 47 3.6 × 10⁻⁴ 4.6 1.54 14.3 5 60** 11g2.5 × 10⁻⁴ 51 3.6 × 10⁻⁴ 4.4 1.45 13.5 4 61** 72y 5.0 × 10⁻⁴ 51 3.6 ×10⁻⁴ 4.1 1.37 12.8 5 62** 85 2.5 × 10⁻⁴ 51 3.6 × 10⁻⁴ 4.5 1.49 13.9 563** 106-10 5.0 × 10⁻⁴ 51 3.6 × 10⁻⁴ 4.2 1.41 13.1 4 64** 122 5.0 × 10⁻⁴51 3.6 × 10⁻⁴ 4.1 1.37 12.8 5 65** 125a 2.5 × 10⁻⁴ 51 3.6 × 10⁻⁴ 4.41.45 13.5 5 66** 130c 2.5 × 10⁻⁴ 51 3.6 × 10⁻⁴ 4.5 1.49 13.9 5 67** 11g2.5 × 10⁻⁴ 55 3.6 × 10⁻⁴ 4.4 1.47 13.6 5 68** 72y 5.0 × 10⁻⁴ 55 3.6 ×10⁻⁴ 4.1 1.39 12.9 5 69** 85 2.5 × 10⁻⁴ 55 3.6 × 10⁻⁴ 4.5 1.51 14.0 570** 106-10 5.0 × 10⁻⁴ 55 3.6 × 10⁻⁴ 4.3 1.43 13.2 4 71** 122 5.0 × 10⁻⁴55 3.6 × 10⁻⁴ 4.1 1.39 12.9 5 72** 125a 2.5 × 10⁻⁴ 55 3.6 × 10⁻⁴ 4.41.47 13.6 5 73** 130c 2.5 × 10⁻⁴ 55 3.6 × 10⁻⁴ 4.5 1.51 14.0 5 74** 11g2.5 × 10⁻⁴ 64 3.6 × 10⁻⁴ 4.2 1.42 13.2 4 75** 72y 5.0 × 10⁻⁴ 64 3.6 ×10⁻⁴ 4.0 1.34 12.5 5 76** 85 2.5 × 10⁻⁴ 64 3.6 × 10⁻⁴ 4.4 1.46 13.5 577** 106-10 5.0 × 10⁻⁴ 64 3.6 × 10⁻⁴ 4.1 1.38 12.8 4 78** 122 5.0 × 10⁻⁴64 3.6 × 10⁻⁴ 4.0 1.34 12.5 5 79** 125a 2.5 × 10⁻⁴ 64 3.6 × 10⁻⁴ 4.21.42 13.2 5 80** 130c 2.5 × 10⁻⁴ 64 3.6 × 10⁻⁴ 4.4 1.46 13.5 5*comparison **invention

It is evident from Table 36 that using compounds of formulae (1) to (14)according to the invention, thermographic recording elements satisfyingall the requirements of high Dmax, high contrast, and minimal blackpepper are obtained.

There has been described a thermographic recording element featuringhigh Dmax, high sensitivity and satisfactory contrast and free of blackpepper.

Reasonable modifications and variations are possible from the foregoingdisclosure without departing from either the spirit or scope of thepresent invention as defined by the claims.

What is claimed is:
 1. A thermographic recording element having at leastone image forming layer, said element comprising an organic silver salt,a reducing agent, and at least one of substituted alkene derivatives offormula (14):

wherein W is an electron attractive group; D is an electron donativegroup selected from the group consisting of hydroxy groups, salts ofhydroxy groups, mercapto groups, salts of mercapto groups, alkoxygroups, alkylthio groups, arylthio groups, amino groups, alkylaminogroups, arylamino groups and phenyl groups having an electron donativegroup as a substituent; H is hydrogen; and two of said W groups form acyclic structure which is substituted or unsubstituted and is selectedfrom the group consisting of saturated carbocyclic, unsaturatedcarbocyclic, saturated heterocyclic, unsaturated heterocyclic and cyclicketone, and wherein said W groups may have substituents.
 2. Thethermographic recording element of claim 1 further comprising aphotosensitive silver halide.
 3. The thermographic recording element ofclaim 1, wherein the alkene derivative has one of the followingstructures:


4. The thermographic recording element of claim 1, wherein the alkenederivative has the following structure:


5. The thermographic recording element of claim 1, wherein the alkenederivative has one of the following structures:


6. The thermographic recording element of claim 1, wherein W is at leastone electron attractive group selected from the group consisting ofsubstituted or uhsubstituted cyano, nitro, alkenyl, acyl,alkoxycarbonyl, aryloxycarbonyl, alkylsulfonyl, arylsulfonyl, carbamoyl,sulfamoyl, phosphoryl, 5- and 6-membered heterocyclic group which mayhave a benzene or naphthalene ring fused thereto, and phenyl having atleast one of said electron attractive group as a substituent.
 7. Athermographic recording element having at least one image forming layer,said element comprising an organic silver salt, a reducing agent, and atleast one of substituted alkene derivatives of formula (14):

wherein W is an electron attractive group; D is an electron donativegroup selected from the group consisting of hydroxy groups, salts ofhydroxy groups, mercapto groups, salts of mercapto groups, alkoxygroups, alkylthio groups, arylthio groups, amino groups, alkylaminogroups, arylamino groups and phenyl groups having an electron donativegroup as a substituent; H is hydrogen; and two of said W groups form acyclic structure which is substituted or unsubstituted and is selectedfrom the group consisting of saturated carbocyclic, unsaturatedcarbocyclic, saturated heterocyclic, unsaturated heterocyclic and cyclicketone, and wherein said W groups may have substituents; and a hydrazinederivative of the formula (I):

wherein R² is an aliphatic, aromatic or heterocyclic group, R¹ and R³are independently hydrogen, aliphatic group, aromatic group,heterocyclic group, hydrazino group, alkoxy group, aryloxy group, oramino group, G¹ is —CO—, —COCO—, —C(═S)—, SO₂—, —SO—, —PO(R³)— oriminomethylene group, A¹ and A² are independently hydrogen,alkylsulfonyl, arylsulfonyl or acyl groups, at least one of A¹ and A² ishydrogen, and letter m₁ is equal to 0 or 1, with the proviso that R¹ isan aliphatic, aromatic or heterocyclic group when m1 is
 0. 8. Thethermographic recording element of claim 7, wherein W is at least oneelectron attractive group selected from the group consisting ofsubstituted or unsubstituted cyano, nitro, alkenyl, acyl,alkoxycarbonyl, aryloxycarbonyl, alkylsulfonyl, arylsulfonyl, carbamoyl,sulfamoyl, phosphoryl, 5- and 6-membered heterocyclic group which mayhave a benzene or naphthalene ring fused thereto, and phenyl having atleast one of said electron attractive group as a substituent.